1st pay all debts(means bad credits leave the good credits like mortgage).
2nd build up an emergency fund , i think it used to be 3 month of your current salary but if you got family then 6month.preferably ibonds or laddered cds. or online savings. i bonds saves you in taxes. any interest you receive from savings or cds are taxable unless/depends on your tax bracket.
3rd if you company offers 401k then max it out. it’s a win win situation unless they offer limited/shitty options/high fees.
4th put it in a ira. but only do so if you don’t need the money until you retire or you didn’t buy your first house yet. otherwise penalties are big.
5th no fifth option since if you only have 300 dollars means you must do the 4 options before. 300 buying stocks would be like gain 30 dollars then throw 50 to dealer. unless you hit the jackpot as google when they opened the stock but then you would not even be able to buy 1 stock…minimum was i think 15000…
check bankrate.com or bobblicker.com