OK...first off you don't need RO! Tap plus dechlorinator (Prime is my choice) is it.
Second...here's a link to some standard tank sizes
. A typical 70g is going to be 20 inches high and 4 feet long. A 2x96W light fixture would be ideal for this setup. If you've got a hood, AHSupply has a great retrofit kit
at a great price. This is just one option. A 2x55W plus a 36W is another option, and so on. If you had an unlimited budget, ADA makes some killer lights
For planted tanks, as long as you set them up right, they are ready right away for fish. The first thing to do is get mulm from someone else. Sometimes the lfs will give you some. Otherwise, ask the folks around you when they will be cleaning their filter. If you time it for the day after the SCAPE meeting at Carl's house, you can get all sorts of mulm
This is the equivalent to seeding and jump-starting the cycle.
For substrate...you've got a few choices. Soilmaster Select is the cheapest clay based substrate you'll probably find locally. I've got a call in to a Soilmaster Select salesman right now (Not Lesco, for those who know). A direct competitor and almost identical option is Turface which seems harder to locate. After that, it gets a bit more expensive with Seachem Flourite, Carib-Sea Eco-Complete, or ADA Aquasoil.