It depends on what your goals are. Pick one and stick to it, for a typical hi-tech like mine I used:
1x 60x30x30 tank
1x 48watt (2x 24watt) t5 luminaire
full co2, this comprises of a drop checker a rhinnox 2000 diffuser, fire extinguisher, a regulator and bubble counter, non return valve and of course tubing.
Substrate (gravel) which is ADA (the best for your money) and sand (as a foreground)
filter I use a eheim 2224 but I'd like a bigger one.
Heater is a hydor inline, better to keep them out of the tank, gives you more space.
Ferts of the dry kind are the best.
optional extras would be lily pipes an inline diffuser and a bucket.