Co2 isn't a necessity, your right. I just barely started doing some pressurized co2 in my tanks and just a regulator set me back $100. But you can make a really beautiful tank just using liquid carbon(its not liquid co2), it does the same thing just a little slower kinda. Just check out Rivercats on AA, she has an amazing 220g 100% planted high light tank and only uses liquid carbon. My suggestion is still make your own ferts though, its saves Soooooo(needs many more Os) much money. The dry fert pack from GLA $30 lasts a year, a gallon of Metricide(liquid carbon) costs about $24 and will lasts a long time too. Just seachem's excel(liquid carbon) cost me $17 and lasted 3 weeks. For starter plants I would check out hydrophila compacta for a leafy plant and maybe some rotala for a fast growing skinny plant, water wysteria grows quickly and looks pretty neat, and of course you can always do some anubias or ferns. My tanks have some of these plants if you want to see what they look like