Just like going to a casino...how much money can you afford to gamble with? to lose?
you can start with [highly speculative] $2-$5 stocks....and there are plenty of stocks under $10
so....a couple of thousand dollars...
if your mutual funds pay a dividend/interest
that is, you are not dripping them
[ONLY 20% !!!...NO MORE THAN THAT!!!]
and use the dividends/interest as "play" money
the first 50% is for your long term, safe, secure investments
the next 30% is for taxes
then and only then, use the 20% to get your feet wet
buy a few shares of a good, "blue chip" stock until you have a 100 shares
then start on the next "core holding"
not as exciting as playing a speculative stock..but long term..much , much safer..
no matter how you play the game
large cap, small/mid cap, speculative
stocks, mutual funds, ETFs, whatever...
have investments that allow you to sleep at night...
if you worry about any investment too much....it's too risky for your temperament...