Ok mate here's a quick run down:
Patch cable (straight-through) used to connect devices such as PCs to switches or routers to switches. Basically, if the devices are different ie a switch to a PC then this is the cable you use.
Crossover used to connect similar devices such as switches to switches, or a PC to PC. So basically, if you want to connect a PC to a PC without any other networking devices involved, then this is the cable to use
Now depending on your networking equipment will depend on what cat cable you want, ie Cat5 or Cat6.
Cat5 can transmit data upto 100Mbps (Fast Ethernet). Cat5e and Cat6 can transmit data upto 1000Mbps (Gigabit Ethernet). Personally I think its overkill having Gigabit ethernet at home, so I would get just Cat5 cable (Fast ethernet).