I tend to pick up Gamepass for 1 month at a time when there is a game I want to play on there. Last time it was Hellblade 2, I grabbed it and played a couple sittings to finish it and then cancelled the sub immediately. I feel that is good value for money since I can check out a few other games in the 30 days.
I wouldn't consider it worthwhile if I didn't have an Xbox Series S though. If my main gaming device was a PC then I'd stick to being patient and waiting for sales. Series S + Nintendo Switch has been a solid combo for my budget gaming needs this gen.