Personally i would wait until the market seems to bottom. Down market does make for good buying opportunities, but one never knows if there are more declines ahead. Moving averages are pretty good at indicating trends. But the risk is still there.
Good luck with your choices.
Yes, $15k for 25 stocks makes for small positions. I’d start small. 15 stocks for $1000 ea. Or as far as $1000 goes. One or two shares of expensive stocks is a reasonable beginning. You can always add more funds later.