Easiest way to find unbundled games in certain price range?

I think easiest way is to giveaway games worth 15$ and released in past 2 months

if you only want to level up for the sake of it (like "here's some trash for you, minions"), buy bundles worth 15cv instead of a single unbundled game.
it's cheaper and "safer" (one game can drop in price and reduce your cv a lot, while multiple bundled games won't affect it too much).

You can use steamdb.info to search for games, but I guess you have to check them manually if bundled or not. Shouldn't be much of a problem since you only want to make a few gibs.

The easiest way is probably knowing how to search in IsThereAnyDeal. You can try this filter, for example:
https://isthereanydeal.com/#/filter:&regular/10/18,&cut/38/80,&drm/steam,-bundled,-wasbundled,-dlc,-package,-steam,-amazonus,-direct2drive,-itchio,-squenix,-uplay,-origin,-battlenet,-microsoft,-type/7,-type/8,-type/6,-pl/vive,-pl/oculus,&steamperc/50/100,-epic,-gog,-gamesplanetde,-gamesplanetfr,-macgamestore,&hlperc/15
This should give you a list of games that are in the 10-18 CV range with the highest chance of being unbundled, at a decent discount, and giving you a key or gift link you can insert on this site.

CLICK CLICK GLUK GLUK
dont forget to click "Show blue discounts only"
example

if all you care about is C.V., I recommend one of two things:
1) dollar bundles with a lot of games. Even though all the games will be on the bundle list,the right bundle of crap might give 7x C.V.
2) newish games that are unbundled but have a good sale. Occasionally you can get an unbundled $50 game for $10, or, even better, a $30 game for $5.

Fallout 4, for example, gives $30 C.V. but has an all-time low of $5.16; Fallout 4 GOTY gives $60 C.V. and has an all-time low of $10.33
and if you don't mind going to grey market sites, the current cost is not too much higher

http://sgtools.info/deals lets you filter deals by SG bundled status.

GG.deals and wait for the winter sale :)

I think IsThereAnyDeal should do the trick. You can just type the price range you want in the right column and click "+". A bundled game would be labeled as "bundled" beside the title. But I think they should add some filters like "never bundled" and "game only(no DLC)."