haha i hear you. If you are playing off a short stack you don't want to take on any too many different alts or you spread yourself too thin. My advice would be to find projects that you are genuinely excited about, regardless of top 20 or not, ignore that.
Once you have that u can further narrow the list down by going for ones that are cheap to buy comparative to your bankroll and have a circulating supply under 500 million or atleast 1 billion.
I never want the price diluted too much with billions of coins unless I really, really like the coins future prospects.
Some Alt Coins I have put money into myself that fit that bill off the top of my head are Ethos, Rchain, Dragonchain, Wax (i love wax), Appcoins, Utrust, Nav coin and don't forget Kucoin Shares to as they will go up this year and earn you a passive income on their exchange just for owning them. Happy hunting