If you choose 15 alts, it is better to choose them from the top 100 markets, because if you look for coins that are in the middle of the market, you can get to the scam
Top 100 coinmarketcap is good (in case what you means from 100 markets is coinmarketcap). At least they are more better than new tokens that full of speculation. Maybe my suggestion if OP want to pick tokens, which already have produdt or roadmap really updated by developer.