Everyone goes through the same concerns when starting out Philip.
I'd be inclined to suggest, rather than investing in the more expensive sous vide bags down the track have a look at a couple of reusable silicon bags. Nicer for the planet and all that. At the moment Anova have a partnership with Stasher and are recommending their silicon bags for sous vide. Currently there is only a small bag available, suitable for a small steak or a chicken thigh, but they will be producing larger bags soon.
Enjoy the fun and experimentation.