Six Flags Magic Mountain in summer

The park will definitely be busy. If you want to be 100% sure you get to ride everything, I would recommend investing in a Flash Pass. However, without one you should be able to get one ride on each coaster, but will probably have limited time for re-rides. Assuming two-train operation (three on Twisted Colossus), I'd expect wait times for the coasters to be:

Apocalypse the Ride: 45-60 minutes (shorter in the morning)
Batman The Ride: 30-45 minutes (shorter in the morning)
Full Throttle: 60-120 minutes
Gold Rusher: 0-15 minutes
Goliath: 45-60 minutes (shorter in the morning)
Green Lantern: 15-60 minutes (shorter in the morning)
Ninja: 15-45 minutes
Revolution: 15-30 minutes (shorter in the afternoon)
Riddler's Revenge: 30-60 minutes
Scream: 30-60 minutes (shorter in the afternoon)
Superman: 30-60 minutes
Tatsu: 45-120 minutes
Twisted Colossus: 45-90 minutes (shorter in the afternoon)
Viper: 30-45 minutes (shorter in the afternoon)
X2: 90-120 minutes (shorter in the afternoon)

For non-coaster rides, expect huge waits for the water rides and short waits for everything else (even Lex Luthor probably won't exceed 30 minutes). In general, expect to wait the longest for X2, Tatsu, and Full Throttle. Twisted Colossus, Superman, and Goliath will likely be toward the upper end of the range while everything else will probably be closer to the lower end. Some rides (especially Viper and Revolution) will be in the listed range in the morning but likely drop out of it mid-afternoon, while others (especially Superman and Ninja) will start out with little wait but grow into the listed range after an hour or so. Green Lantern, Lex Luthor, Revolution, Riddler's Revenge, Twisted Colossus, and Viper all offer single rider lines and these can save time if your party doesn't mind splitting up.

As for a touring strategy, due to the newness of Twisted Colossus it is difficult to say what the best route is. A lot of people will go to Twisted Colossus at opening, but due to the capacity and lack of nearby attractions they are usually dispersed by 1 P.M. and the line will be shorter. In addition, Twisted Colossus doesn't always open on time. Therefore, I would recommend arriving at least 30 minutes before opening and picking one of the following options to start your day based on the situation.

Option 1: If X2 can be seen testing, go here immediately at opening. After riding X2, proceed to Tatsu, then climb Samurai Summit to ride Ninja and Superman.

Option 2: If X2 is not testing but Twisted Colossus is, go directly to Twisted Colossus. After riding both it and Scream, climb to Samurai Summit and ride Superman and Ninja, then head down to Tatsu.

Option 3: If both X2 and Twisted Colossus are not testing, go directly to Full Throttle. After riding, take the Orient Express to the top of Samurai Summit and ride Superman and Ninja, then head down to Tatsu.

After completing one of these three options, head to Apocalypse and work your way around the park clockwise, stopping at attractions as you reach them. If you are interested in the water rides, do them as early as possible to avoid lines. Try to hit the big coasters in the 2-5 P.M. window as this will generally be when lines are shortest. If you are forced to prioritize, I would consider the following the must-ride list for the park:

Apocalypse the Ride
Batman The Ride
Full Throttle
Goliath
Lex Luthor: Drop of Doom
Riddler's Revenge
Roaring Rapids (only if you want to get wet)
Superman: Escape from Krypton
Tatsu
Twisted Colossus
X2

Lastly, have fun. If something happens that you didn't anticipate, just adapt and go with it. Also, remember to stay hydrated. You'll be riding a lot of roller coasters in 90+ degree temperatures, so don't let unexpected illness end your day prematurely.

Thank you really much AJ! I appreciate how much efford you put into that! I still don't want to buy a FlashPass, because 160$ for the regular and 280$ for the gold FlashPass is just way too much money. Maybe there is something like an "early entry" because I heared of that at other theme parks. I rather would do that if it isn't expensive. Thank you for all your effort!

Discover Card holders can enter through an exclusive gate, which can sometimes get you through security faster. Gold Season Pass Members can also get in early, but aside from buying a Season Pass, there's no way to buy early entry into Magic Mountain.

I'm not sure how big your family is or how many of the different rides they will want to ride, but if this is your first time to Magic Mountain, I would focus on experiencing the best and most unique rides/coasters on this visit (X2, Full Throttle, Tatsu, Goliath, and Twisted Colossus), and worry about the rest of the park on a future return visit. Magic Mountain is easily a 2-day park for a first timer (3-day park if you're visiting on a Saturday).

Bring lots of patience for those hour-long lines and tolerance for the throngs of discourteous teenagers. Be grateful you're not planning to go on a Saturday, where you'd be lucky to get on 7 rides in a full day.

Like Russell said, you need a Discover card or Gold Pass in order to get early entry. You only get in 10 minutes early so it isn't really anything worthwhile and it would actually be cheaper to do regular admission with a Gold Flash Pass than to upgrade to Gold Passes. The Flash Pass is expensive and I would not buy it unless necessary, but if you only have one day and will not be returning to the park for several years I would absolutely budget for it just in case. You'd probably be happier spending the money and doing everything than missing out on something, so do a few rides and if you find it's taking longer than what I listed above I would absolutely recommend grabbing one (even if it's just the regular). Even if everything is at the low end of the ranges I posted that's still 8+ hours in line, so if it's significantly busier you'll miss stuff without one.

Also, I'm not sure how strict your dates are, but if there is some flexibility I would advise waiting until later in July to visit. Goliath has been closed since early April due to a broken lift hill chain and due to a manufacturing delay the replacement still has not arrived. It is likely at least a few more weeks before it reopens, so if you are able to wait until late July I would do so. Crowds should be pretty consistent between now and mid-August so that isn't a factor to worry about.

We are four people from Austria and will do a road trip from LA to Seattle. We will arive in LA on 07/22 and want to do a lot and a few hotels are already booked. So we don't have a lot of flexibility and will come back to SFMM maybe in a few years. If you say it is that crowded we maybe really consider about buying a FlashPass.
The only big theme parks we were at were Europapark in Germany, which doensn't even offer something like the FlashPass, and Garaland in Itay. In both parks we almost never had to wait more than 45 minutes, actually the most rides were less than a half an hour to wait, although both parks are great.
Thank you guys for all your quick replies, I really appreciate your effort! I will think about buying FlashPasses, but anyways we will have a great time at Magic Mountain!

Those dates should be late enough. I was more thinking if you were visiting at the beginning of July and could delay it then it would be a good idea to do so.

While I haven't visited any European parks (except Disneyland Paris), from what I've heard I can tell you that SFMM will be a very different experience. In the US, the major regional parks focus primarily on high thrill attractions and much less on theming. Some areas of SFMM are nice (especially DC Universe), but you'll also see rides that are simply built over a parking lot. The park is still enjoyable, but you should go with the mindset that it is primarily a roller coaster park (or iron ride park as some call it) and not a fully immersive experience.

Another thing that differs in the US is that efficiency usually isn't as stressed, with hourly goals on the big coasters in the range of 800 riders per hour (or less on rides with lower capacity, such as Full Throttle, Green Lantern, and Superman). From what I've heard, somewhere like Europa Park will generally run all available trains and get them out as quickly as possible. At SFMM, even on coasters with three trains, you will never see more than two being used (except Twisted Colossus) and it isn't uncommon for trains to stack on all but the longest coasters. Part of this is to save on maintenance costs, part of this is due to super-strict safety procedures, part of this is due to slow guests, and part of this is due to uninterested employees, but all of it contributes to the longer wait times. Like I said, see how much you get done in the first hour or so and then decide if you'll need a Flash Pass to do everything you want to ride. The park has gotten better about posting wait times at the queue entrances in recent years, but assume that it could be up to 30 minutes off in either direction and that a line will take about twice as long as a similar line would take at Europa Park.

Thank you very much for all your effort guys!