I just got my father a pc and he plays stuff like the 90's Hoyle Board Games and Hoyle Casino and basic card games like solitaire or poker. Are there any of these types of games on GOG that are fairly cheaper?

Zachatronics Solitaire Collection
Ancient Enemy
Shadow Hand

The answer is no, I'm afraid. There are a few exceptions (some chess games, some kind of old Viking board game, a solitaire or two) but in general you won't find classic board or card games on GOG.

Not really.
But I can recommend Balatro, PySolFC, and whatever you find suits you on the LibreGameWiki.

Does he know PokerTH? It's free.

Solitaire Quest
Telltale Texas Hold'em

Or something with dice: GNU Backgammon

Would love if GOG could get the Hoyle card game collections that Sierra released back in the day, those have some really amazing music that just really helped you zone into the game and really relax.

By that definition, why not even suggest Gwent? :P It's pretty clear the ask is for the likes of "101 Solitare Games Pack", so apart from the Zachatronics Solitaire Collection, I think there's only this:

https://www.gog.com/en/game/solitaire_quest_garden_story I'm more of a Mahjongg fan myself, but there's some lovely tile matching games in that genre they could explore bringing here also.

Tile matching Solitaire Mahjong is nice, but there needs to be more of the action mahjong too. Besides, I already covered that in PySolFC.

That'd be a great day if gog had all the Hoyle Board Games and the Hoyle Casino games. The only issue I can see is the licensing of the voice actors, the banter and insults from the AI really made the games shine.
I have installed Hoyle Casino on a win10 pc and it runs but it runs in a 90's Nokia cell phone screen sized window.

Speaking of, if someone could revive MPV Software and get their games that'd be a nice trove of card/board games too.

(Especially if they were stripped of all the old eGames trappings.)