What I mean by decent is where you can really see that it is growing and it can give you profit that is enough to be reinvested.
Call me dumb but I really don't know. I'm sorry.
My only source of coins is my signature campaign. I earn about less than 0.1 BTC per month.
Any advice would be much appreciated.
you shouldn't really ask this from other people, and instead come up with the answer yourself.
because it is up to you and your pocket + willingness to take risks that can answer your question.
for example if you have 100
BTC and want to take small risks you can go in with 10
BTCor if you have 0.1
BTC and willing to take big risks you can go in with all of it.
also try to think in fiat terms that might help like 0.1
BTC=63$ so are you really worried about losing 63$?