A fine-line sharpie is a great beginner's tool for panel lining! It's a very basic trick to really make a kit pop and a great starting point for going beyond a straight build. They have dedicated paints and markers for this but a fine-line sharpie works. Go over the details engraved into the parts with it, and wipe away excess with some rubbing alcohol on a towel.
Good luck!
Video I recommend : https://www.youtube.com/watch?v=WOmZbU1i90E
Example of panel lining comparison :
The one that got me I to Gundam was Wing Zero from Endless Waltz, so I have a huge soft spot for that one. Other ones I really love are Unicorn, Barbatos, and GP-01.
Outside Of Gundam, I like Laevatein from Full Metal Panic, the designs of the Flight Units from Nier Automata, and GaoGaiGar.
Really looking forward to Armored Core 6!