i want to get a tank but i need to know which i should get i think i should get 1 filter and sump AND protein skimm
No need for a filter with a sump/wet dry filter. If you use live rock then you will not need filter media for aerobic bacteria. If no live rock then you can add bio balls, sponge whatever directly to the sump.
You can also place bags of carbon in the sump if needed. They are great for keeping heaters and other equipment in as well. The protein skimmer is a filter as well. It removes things from the water before they can break down to ammonia. So no, no need for a filter with a sump and skimmer.
Your sump will serve as your filter. Your sump should have at least two chambers for filter medias. On the first chamber you should have a layer of mechanical and the rest including the second or so chamber you should have bio filter media (ceramic rings work best for me). In your refugium area you should put whatever you want (live rocks, etc). Next chamber would be for the skimmer then some bubble traps and finally the return pump. Having an extra filter is good but it is not worth since the sump is your main filtration
The sump generally does contain a mechanical filter media such as spunge. Live rock and live sand serve as your actual filter though . Sump or not, if you have 1.5 lb of Live rock per gallon of water then a filter is not needed. The average sump will handle any large debris in the water. I don't have a sump on my tanks so I prefer to use a filter just to keep a bag of carbon in.
