The seven ribbons you can earn during a match are these listed in order of best for this achievement:
Spotting an enemy for the first time:
Enemies you spotted damaged by teamates:
Causing critical damage to enemy crew or module:
Kill an enemy:
Tracking an enemy that is then killed by a teammate:
Capturing base points/capturing enemy base:
Since damaging enemies is excluded, you're limited to earning 20 ribbons of the other 6. Spotting ribbons are by far the easiest other ribbon, so you'll want to use a light tank for this achievement. Use a light/scout tank of your choice(choose one that has a high sight distance), and I would highly recommend adding the extra vision distance equipment with silver so that you'll be able to spot enemies before they see you.
Widepark is an excellent map for this, because you could get up to 15 ribbons right away if you're the first person to look over the railroad tracks. Just make sure you get out of sight before you get hit. Then, drive along the top of the railroad tracks spotting enemy tanks, and you'll get your ribbons very fast!
Otherwise, on any map, work on scouting for your team(find a good forward position and hide in a bush or behind a tree, etc), and you should get both spotting ribbons and spot assist ribbons easily. Crew/module damage and tank kill ribbons should be just secondary focuses, with tracking tanks and base captures last. Damaging enemies is useless for this achievement so it's actually better to not shoot as you'll lose your camouflage cover and your extra sight distance bonus from staying still.