Originally Posted by khoornix
I just received mine and i'm pretty dissapointed as the terrible cai os
Yes, "caios" is pretty awful.
Flashing tool for official roms is SP Flash Tool, the same as for all other phones based on the same processor. There are threads here on how to use it if you need to.
Custom ROMs are flashed through recovery, and to install recovery you can either use flash tool with the attached files, or more simply root the phone (motochopper autoroot works ok), then install mtk droid tools (thread here on xda) and flash or create a new one from there.
Once you have done that, ROMs are here
. You will need to register a user account, but it's pretty easy with google translate. LeWaOS is the one I prefer of the custom ROMs on that site.
CWM recovery and boot image attached below