If I buy a game as a gift to my friend, the game price will count as his steam account value?

If you mean to join steamgift yes it should (and he activates it)

If he add game to library then yes, he will be able to join SG.

His acount's value has to reach 100$. It doesn't matter if you buy for him, or he buys. Only the game's value matters.

Even with the free Total War weekend? I thought Steamgifts wasn't capable of eliminating the free weekend games from the $100 requirement. The Total War games would put any account through the limit on their own if that's still the case.

I did see a new member yesterday with zero games on their account other than free-to-play ones, not even a bundle game.

Just buy them whatever is cheap on Stream right now if they not care,or if your feeling froggy you can buy him a game in his wish list either way as long as it is enough to reach 100 he will be fine

The only time giving a gift will not count is within steam itself activating a gift does not allow you to by pass the 5.00 steam limit to access friends and such on new accounts

I should have added that also like flag said,as long as they have not been bundled

As long as it's not on the bundle list.

Thanks for the quick reply, guys. He got one of the free keys that PC Gamer is giving, and he is now allowed to join.
If you're interested: http://www.pcgamer.com/get-a-free-key-for-grimoire-manastorm-with-bundle-stars/

remember to sync the profile after activating the gift.