It will be enough. Make sure to use all dailies, rebates and events to their fullest potential, because most of the time using events correctly gives you more income than recharging small ammount for monthly card. That being said, if you do mentioned, you should easily end up in top3.

you wanna start on a new server, i say get iruka very good at the start gives a good amount of power. 2 star is fine 3 if you want, DONT go for RNG events. save your coupons and wait for a godo event like lucky board or the sage event. i wouldsay get guy he only 2-3 seals. If you want you can get the medal and monthly for extra xp and 70 more coupons a day. all in all, i would say wait for your server to start getting rebates for recharging so dont go like very heavy at the start. just enough to get ahead. So all in all, i say maybe 100$ if you start on a new new server. you can get Jonin medal, Monthly and 2 star iruka. you get more with the new server events too so youll get tool and coupons and magas and stuff.

Thank you for your answeres so far.

Another thing: Which main would be the most efficient to start with if i get gaara and naruro from my purchases? I read fire is good for the start but weak later, but i didnt really inform myself yet properly.

Lightning/fire are the easiest ones to level to 60, then you get the option to change class. Id lean towards lightning, because you c*e guy, iruka and blitz through everything. Fire takes extra turn there, but is insanely annoying early with his mirror and debuffs in the kit.