Compendiums for modules

Hello, we are just about to start Lost Mine Of Phandelver. First module for us and all are pretty green. Do the modules contain everything needed? Any benefit to buying any Compendium at this point? Buddy created a game on Tabletop Simulator as a first Time DM but very tough. Kept telling him to come here and just purchase something like Lost Mine. Any suggestions? What will he need if anything else or what will make it even easier or enhance the experience?  Xanthar’s, any other D&D download? We have 5 players. 6 too many? Appreciate any input.

The module has everything you need. Buying a compendium like the Monster Manual would make customizing easier, but if you plan as running as written or only making minor changes, it will do you fine. The PHB is probably most useful in this case, since it will give your players the full range of base classes, races and spells. Again, not necessary, since you fill in anything character-wise manually. Just easier.