First of....WELCOME TO MAAST!!!

You do not need a sump for a 30 gallon Aquarium.

What are the dimensions of the tank?
What do you plan to keep in it?
Fish only? Or corals?

You need a skimmer. The can do as easy as a HOB (Hang on the back) skimmer.
Like this one:
http://www.premiumaquatics.com/Merch...ory_Code=AquaC
or this one:
http://www.premiumaquatics.com/Merch...ry_Code=Bakpak

Those are just two of many.

If you still have room on the back of the tank a HOB refugium is a great addition. This will help keep your water parameters in line and supply the tank with pods. I like the CPR HOB refugiums. They come in several differnt lengths. Get the biggest you can fit.
http://www.premiumaquatics.com/Merch...y_Code=Special

Now all you need is a light and some power heads. The light will depend on what type of corals, if any, you want to keep.