Sump filter is best if your tank is design for it. i.e. with overflow system. If the previous owner advice canister filter, then I suspect that the tank is not design for sump system.
Basic filteration system includes mechanical, chemical and biological.
Basically, you need filter wood or filter sock (mech) to remove those solid waste and a protein skimmer (mech).
The next level is to have some media where bacterias can colonise, live rocks are good. I used other biological media like biohomme for the BB to colonise on top of live rock.
As for chemical filters, I personnel don't use them unless necessary as I find them a bit troublesome. Some pple will use active carbon (charcoal) as a chemical filter to remove unwanted/harmful chemicals in the tank. Do note that active carbon needs to be change regularly (a reason why I don't use them as I'm lazy) as once they are saturated with unwanted chemical, they will release these chemical back into your tank system.