Consider a Skimmer an investment for all future tanks! You can use a skimmer for freshwater and saltwater. If you want a Dwarf Lion you will need a Skimmer, no ways around it. The one I linked is a good skimmer, and it's worth getting.
When I started my tank, I had nothing! I spent well over a thousand dollars for a 29 gallon tank. When I upgraded to a 55 gallon tank, I spent only 300 at the most, because I had everything already. All I had to do was get some more sand and rock and the tank.
Live rock is an investment as well, as you can almost always sell it for the price you bought it, and you can use it forever in newer tanks you upgrade too. So if you look at the skimmer and live rock as investments, than it really is cheaper than it sounds.
I wouldn't skip out on the Skimmer, OR the Live rock! Having at least 50 pounds of rock is going to help you tremeindoudsly in filtration, and that's around $200 well spent!!
The cheaper way of course is to just get base rock, and overtime the rock well become live. That is cheaper, just buy some base rock, and a few pounds of live to seed the base rock. For 50 gallons, 50 pounds of rock is good to have!! I had 55 pounds for my 29 gallon!
This is Dry Rock!
Get your bulk of rock dry! Than seed it with a few pounds of life rock.
should have live rock, so you don't need to order it online, your LFS
should also have base (dry) rock!