well the single most important thing you can do is to add another z-screw.
Some cheapo kits around and plenty of solutions on thingiverse.
https://www.thingiverse.com/thing:4373101

Thats pretty much the biggest issue with most of the creality i3's.

Once you've got a stable x gantry - you convert to direct extruder and then you've got a printer :-)