What words can you use as an adverb?

There are many. Here are some examples:

adverbs of time: today, soon, first, later, next

adverbs of frequency: often, never, occasionally, seldom

adverbs of place: here, there, below, down, indoors, outside

adverbs of manner: gracefully, quickly, badly, sadly, carefully, quietly, happily

adverbs of degree: very, quite, somewhat, too, not, extremely

Note that several ending in LY are forms of an adjective. One way of forming adverbs is adding LY to the adjective form, e.g. obvious-> obviously, even->evenly.