if you are talking about putting funds into a 'bank' which promises interest, where you do not have to do anything but wait.. id say they are 95% scams. you best bet is to continue gaining more small amounts the way you are now, just hold them yourself and in a few years the value will naturally be worth more than now.

the only legit investments i do is in proper businesses (VC investments) bt that involves getting personally involved with the company and doing proper contracts.  however for small 'dust' amounts like you are hoarding, there wont be really any proper contracted investment openings for you.

so just increase your bitcoins and hoard till bitcoin value increases