Hindsight is a bitch alright. I had 300 ETH bought in the ICO, I sold all around $3 each and I thought I was a genius with all that 600% profit. And then years later on even with this Ethereum downtrend, I wish I waited for much longer.
Sorry to read about your investment mistake. We all make them, we cannot win them all. Sometimes we sell early and sometimes we hold on to them for too long.
Do you remember how much you paid in the ICO for the 300 ETH?
It should be around $90 - $100. As far as i know, the ico price of ethereum was around $0.31
This is a very old ico but some new sites have already made the detail of ethereum ico like this one
https://icodrops.com/ethereum/It looks like ethereum ico is not offering a bonus mechanism for early investors or i may wrong about that because there's only a little information about that but it does not specifically explain a lot about ethereum ico and there's a bonus mechanism or not.