A land with a basic land type can't be included in your deck if that basic land type's intrinsic mana ability generates a color of mana outside of your commander's color identity
The likes of the "Spellslinger" Starter kit is no more than a couple of dollars/euros/pounds and often gets given away at events
Dominaria, Innistrad and M12 all provide solid cards that can fit in most decks, as long as you disregard the cards that depend too much on synergies (UR wizards,Burning Vengeance,Tribal cards from Lorwyn, etc.)
If you cast a creature spell you don't own, you may still choose to sticker kick it
But its still a precon deck, and there are always a few aspects which can be cleared up with a few extra singles at minimal cost and make it feel substantially more consistent at the tabletop
Dread Presence Dread Presence offers beneficial options whenever you play a swamp