Which is better: Invest my Bitcoin on legit mining sites and purchased power before the halving because it is currently cheap or save my bitcoin and trade it after the halving because its value might be doubled?
Better purchase bitcoin during halving and go trading, than investing it on mining site. You can gain high in trading 5% to 10% per day gain is good.
entering trading without experience means losing -5% to -10% per day instead, trading is a good way of making profit but it needs some expertise because it is a hard thing to do.
and also i want to add that investing in mining sites is the worst idea you can have for an investment.