Please give me guidance!

Heya, I’m looking to buy a 6-month subscription but the prices are really high in my country currency (I’m brazilian) and I really don’t want to get into BfA stuff. Sooo, I was thinking… Should I get the 6-month sub without any expansion and try to farm the gold for tokens and then exchange them for Shadowlands expansion on Blizzard Store when it releases? (BfA should be free then, so I shouldn’t need to buy it before buying Shadowlands right? Do I have the time to enjoy the game and farm the gold I need?)