The most important advice I can give is, don't have the vehicle you are building and wheeling be your only vehicle. Get a daily driver beater. Something dependable, it doesn't have to be cool, cause the 4runner is cool. This way if Monday comes and you have a stripped control arm bolt from working on it, or it's broken from wheeling it, you can still get to work or school. Mishaps like that are very common.

If the reason you want a 4runner is for off roading, get a 4x4. 4x4 > 4x2. Yes, you can still have fun in a 2wd. Yes, 2wd with locker is surprisingly good. But not as good as a 4x4. You won't be doing any crawling in a 2wd. A 4x4 unlocked is slightly better overall then a rear locked 2wd. When it comes time to upgrade, switching out a diff will be way easier then converting to 4x4.