Separate your money for living and investment, if that 4k is for investing then, you can buy BTC now try to buy for lower price, and don't think of spending it, try to hodl at least 6-8 months from now, hodl is the best way for investment in BTC. Though there's someone who will tell you to trade, sure, if you know what's the success way of trading then do it, but if not, then hold is the recommeded choice.

Just to make sure that you use a secured device for hodling the BTC you have, at least desktop wallet such electrum in safe and malware-free desktop or a hardware wallet such ledger and trezor.