Nice! You're in for a quite treat! I'm a games series fan, but never read the books. The 3rd game should be okay to start.
Any tips? Well, yeah: read the descriptions, use the Signs, use potions, read the Beastiary, brew monster decoctions and find the ones that will fit into your gameplay style and be useful (I found relying on the Quen Sign, wearing heavy armor to be more forgiving). Some might be worth it, others are situational. Oh, and don't rush the combat, got hit - block/dodge/roll away first before making a counterattack.
Enemies (both humans and creatures) behave differently, so might wanna spend some time waiting for them to show off their moves first, but all should be in the Beastiary. And if you don't feel like reading that - don't worry, you'll figure it out.
Money will be no issue, resources are aplenty, so no need to hoard stuff and don't afraid to use it. Repairs better be done by the weapon/armor repair kits that you find, blacksmiths will bankrupt you.
Might wanna try to start Treasure Hunt missions, if that's in your level range. Worth it.
I don't know how easy/hard the game should be for someone who hasn't played much games, but you should be fine.
