You'll need some sort of filtration in my opinion. Mechanical at least for getting particulate matter that youre skimmer shouldnt and cant get to.
If it comes down to it you can easily use a hang on back filter or a canister filter if you aren't wanting to do a sump. I have a canister on my 55g and all it needs is to be properly maintained.
Also a filter will be a good place to put any chemcial filtration media such as GFO
if you need it or carbon.
In addition, if you wanted to forgo any filters then I would say to up your rock amount by ALOT. It will act as your primary biological filtration in the tank. It's recommended to have 1.5 to 2.0 lbs per gallon.
Hope that helps