It seems to me that you need to make investments in the cryptocurrency that has the most stable exchange rate.
It's not, it's not stable at all.
Every token in the coinmarketcap , coingecko or even newly listed are all deserving of investment one way or the other. So for you to invest in crypto currency you need to define your kind of investment, is it short term gains or long term; because 200$ is not enough to lay a claim to massive investment option. Always do your own research.
If you invest your $200 in Ethereum when the price was below $200 then surely you can get your return back + profit in 3 months if you do long term, but for this price range I would suggest to invest in another crypto or do short term trading if you brave enough due to how hype the price is and the volume is really high so the liquidity is really important here.