This is not a question that someone can answer by saying this or that coin.
My suggestion is that you should spread your available funds in various coins.
If you are a long term investor put 50% of your investment in top 10 coins ,30% in lower coins and keep a 20% for day trading.
Regards.
agree with this, you need to decide what alcoin are you going to invest in. You need to get to know the tech behind these projects and invest in projects/coins you have faith in. I believe you cannot go wrong with nearly any of the top 100 coins, not at these prices anyway. but that is just my opinion, you have to do research for yourself to see in which one you believe in the most.
to answer your question regarding whether to buy cheap (per unit coin) like ADA for example or more expensive one like ETH for example I would like to say,
multipliers are the same regardless of what the unit price was. so if both of the coins went up 5x and you had equal investment(fiat or btc) in both of them, then you get same profit off of them too. hope that it makes sense...