Sous vide - add liquid or no in the bag?
Generally speaking meat that is cooked sous vide does not have marinating liquid in the bag, though a small amount of fat (oil or butter, for example), might be added to help with air displacement.  A lot depends on what you want to achieve and the specific cut or protein you are cooking. There are several ways you can go, but dry-rub or marinate...pat dry or wipe off...quick sear...bag...cook...final grill or final sear...is often a good practice.   A vacuum sealer is nice to have for extra long cooks, when you get into the multiple day range, but is not really necessary for most applications.  There are many online resources you can check for guidance.