FWIW,
Common mistakes:
1. Not considering the future use of the controller
2. Inadequate power supply
3. Second rate / problematic drives
4. Inadequate stepper motors
So you buy all at a bargain and save $A.....
Then you rebuy and to get what you needed or wanted in the first place $B
So $B - $A= may be nothing but agrivation and wasted money
Take you time, build the controller yourself, buy once and save money, know how it all works and can repair it, ....nice good feeling........$ cost in the long run = priceless
You CAN do it all......,
RICH