The easiest way to trade Bitcoin is the basic buy and sell model by using peer2peer trading which can grow your coin stash in no time and I think this is the best!...
If this was a really fast way to increase the amount of BTC in the wallet, then everyone would only be engaged in P2P. But in fact, everything is completely different from what you write, since at any moment the price may change and you may find yourself in a position where bitcoins are sold, but you will need more stablecoins to buy them than before.