The grade 1 gifts will cost 35k to get from 0 to 6000 and are definitely recommended as the first step.
The grade 2 vendor gifts will cost 60k to get to 8000, and if you bargain-hunt for grade 4-5 blue gifts from the GTN you can get to 9500 for less than 60k. It's all in the fact that single grade 5 gifts reward 190-200 points, and grade 4 give 140 or so. MUCH better than the 19 points you get from a grade 2 vendor gift.
Seriously, a grade 5 gift rewards as much affection as 10-12 grade 2 greens, so it's worth 6k credits. Yet I see grade 5 gifts on the GTN for sale for 2-4k.
But, whatever, it's your money, spend it however you want.
I maxed out Vette, Jaesa, Talos, Khem, and Xalek. Rank 5 gifts that they actually liked were few and far in between, and were almost always extremely expensive. They only give big affection numbers if there's a significant difference between your current affection level and the rank of the gift.
5-6k credits for a gift that gives 48 affection is not a great deal, and you'll mostly find those on the GTN, especially when you factor in that there aren't that many worthwhile professions, so the comps that gives bonuses to bioanalysis/slicing/etc drive up the price of gifts that they favor.