Do I need to use a vacuum sealer?

Only if you already have one, or you plan to store food without refrigeration for a long time. It's not something we think is absolutely necessary, and we don't use a vacuum sealer terribly often since it's easier to just use zip top sandwich bags and freezer bags. Vacuum packed food becomes a rigid unmaleable shape that does not conform well to your bag, bear bin, or any other container. While it compresses the food inside the bag, once you stack them together it creates a lot of wasted space between each bag since they don't seat well with each other.

However, if you do choose to get a vacuum sealer, don't make the same mistake we did. Get one with a built in holder and cutter for the roll of bags. It's a total PITA to cut those bags straight and even with scissors.