>>5330620I bought the game a few weeks ago and that depends on whether or not you want 100% complete it or if you want to just play through the single player/co-op mode casually. You can do the latter with just a Land vehicle but the former will require all three vehicle types.
There's also the issue what 100% completion means to you, there are some areas that require you to have a vehicle with one of the eight alignments to access, but those areas are just extra challenges that can be skipped.
But I recommend that, if you're buying it used, you get more than one Skylander figure. Just having one means that you'll have to start a level over from the beginning if you end up dying in it.
And since you're a noncollector, you won't have to worry about bullshit like Dark variants, patina finish variants like pic related, and the three different varieties of Hot Streak.