This is my hobby as well. I stuck with fresh water, because frankly there seems to be less complexity in setup and more room for error. I totally understand the excitement about everything fish related hehe. The stocking possibilities are endless with fresh, the plants, shrimp, snails, and of course fish. Put together fish and plants from five different continents, or build an accurate biotope. Monster or nano?!
The truth is-even though I have kept fish for a bit over 2 years, I have been researching for at least 5 years-the funnest part of the hobby in my opinion. Putting it all together requires some deep reading and research, and the planning part doesn't cost anything! There are massive communities to draw info from and share stories with-it free as well. Tons of YouTube videos and how to sites to browse.
Where can you go from here? One of two paths-constant optimization-aquiting equipment piece by piece to build the perfect tank, or learn to DIY your pieces. In the fishkeeping hobby there is no "standard" anything-your filter can be canister, hang on back, swirl filter, radial flow, sump (like five different types of these), or even deep sand beds (for only the brave).
Damn I need another tank!