dry ferts are a lot cheaper. I'm running a 100gal and if I used liquid ferts, I'd be paying £10 every 2 weeks. I've just done an order on the internet for a years worth of dry ferts, and I've paid £65approx for the lot.
When I first planted my tank I knew nothing at all about plants. So I got a tropica catalogue off ebay. Great book - huge variety of plants, and a description of each, with requirements.