Installing gapps/rom

[jsmoke]

I don't have an sd card and the twrp I've installed only allows for adb or sd card although I have seen twrp version that seem to allow to install from internal storage.

Firstly I assume you can't install a rom via odin?

I'm going to try the adb method but also need to install gapps, do I just install gapps in the same way as the rom and after the rom is installed?

It's

adb sideload "C:\yourROM.zip"

I think.

Also don't I completely erase the phone first in twrp or just the caches?

 

[biron_w]

Your best asking these questions on XDA. Different phones have different ways of doing things.