The stuff that deals damage needs coins? All of the weapons that you buy with coins can be bought with vouchers! The two star weapons aren't even bought with coins, they're bought with medals.
Of course the stuff you get at the beginning expires soon. It costs coins and you get it for free. You have to buy voucher equipment for a long time and convert the stat boosts from the coin equipment to the voucher equipment. When the voucher equipment does expire, you can just renew it.
Pfff! Supporting the developers and helping them make the game better?! Who ever heard of such a stupid idea?! I agree with dragon! (In case you didn't notice, that was sarcasm.) XD