Here is a list of what Types of Gifts yeild the most affection gain for Mako. Theese held true with grade 1 and 2 gifts, so I'm assuming the types wont change.
Mako
Best- Technology ~ 96 affection
Better - Underworld Goods ~ 48 affection
Good - Luxury, Weapon, Trophy, Cultural Art ~ 24 affection
Neutral - Republic Memorabilia, Military Gear, Courting ~ 0 affwction.
I'm not sure if other companions have the same "patern", but I'm interested to know. By patern i mean 1 type is the best, 1 is pretty good, 4 are meh and 3 are a waste. Will post more if i find time.