This depends on the project itself. If I see a lot of potential I am willing to invest more, but for projects that only have a certain level of potential, and dont look that promising to me, I rather go in with a little money, just in case it takes off. So that I dont loose out if it does. In most cases I go in with around $250 - $500. But this strategy also failed in more cases then it did work out, most of these ICO's I invested in are now below ICO price and I would have had a lot more gains if I just stayed in BTC. But thats the risk.