"I buy all sorts of things."
Just take this sentence as 色々(な物を)買います. As everyone knows, Japanese is a very contextual language so it tends to omit "unimportant" words. In this case, "thing(物)" is not important because you can only buy, well, things.
I can imagine this sentence is used, for example, as an answer when someone asks you what did you bought (何を買いました？).
Alternatively, you can say いろんな物を買います, which has the same meaning.
That's just what I understand though.
I would also like clarification on this sentence. 'Iroiro' is a 'na' adjective, to my understanding, so I can see it being both a noun, in which case it should have 'wo,' or an adverb, in which case it should have the adverbial marker of 'ni.' Regardless, I don't think this sentence is grammatical.
Japanese here ( = Duolingo) still seems to be in beta, and it definitely shows. Probably, not many real people are working to make this course, and using machine translation? Some things in English do not make sense, some things in Japanese sound unnatural (according to my native Japanese help :) ).