GBR's do fight a bit, but it's nothing compared to there bigger cousins. In a tank your size it will probably be a chase and a bit of fin flaring, nothing to serious, more so when eggs have been laid - just put loads of plants, bogwood caves etc and you will be fine. A tank that size filled with GBR would be a stunning tank. Can't recommend you fishless cycle any stronger, it will be a lot of work in a big tank - but well worth it, you could do a fish in with loads of Tetra which you will need anyway for the GBR - dither fish is a must with Cichlids. Male female ratio won't be to important until on down the road when your tank is nearing fully stocked, just look for matched and unmatched pairs and add accordingly. If you allow 30cm by 30cm for each breeding site you should be okay, in the end you would want more females than males and dont mix species ie gold ram with GBR or electric blue, you will get messed up looking fry. IMO feed them on New Life Spectrum Cichlid pellets for there best colour and health, or New Life Spectrum Thera A - my GBR love boiled deshelled peas, really good for them and I bet you yours go crazy for them to when you get them. You will probably need a mid sized group of substrate cleaners, I'd recommend 10 Sterbai or Julii Corydoras - my GBR get on well with them. I've also found the variety of Rams that are called German Rams, or sometimes labelled Wild Caught German Rams, like the one in my profile pic are far hardier than the Asian type that come from dodgy breeding processes, the Asian rams do look stunning with the really deep blue and fire red but are a hit and miss even here in the uk where the Rams are generally hardier the US stock.