I personally don't like base rock either because most of the stuff LFS sell are really dense (ie. heavy) so although you save $ per lb, you might not save much by volume. Also, good LR is usually light because its porous, which increases their usefulness as biological filters. If the base rock is really dense, not much space for the good bacteria to grow, is there.
I would buy what LR I could afford & leave space to add some nice pieces later since you'll most likely find some beautiful pieces available when people get out of the hobby or downsize.
My macroalgae grow inside my display tanks, not inside a refugium. The macro are great for nutrient export & I can sell or trade the excess halimenia/prolifera/other caulerpa; whereas, I have trouble selling the brown goop from a protein skimmer collection cup
It also provides my pods & mysis shrimp lots of places to hide, eat & breed. Like Albert previously mentioned, it will depend on what you envision for your tank. If you're going for SPS or other corals that require pristine water conditions, then you might be better off investing in the best protein skimmer you can afford. If you resist the temptation to put in a lot of fish into a reef setup, your nutrient problems will be greatly limited. If you have the lighting for it, clams are also great biological filters. JME.
Anthony