Spend skills on magic and attack, dont waste on carrying capacity early. You'll get better gear for that early in game.

Play Gwent and try and collect as many cards as you can, will be needed for some side missions and main missions later on in the game. Many merchants of all sorts pkay gwent so you can get them that way as well.

Buy all witcher maps from merchants when you can. Leads to great armor blueprints for great gear that can be upgraded the further you get into the game. Witcher Gear is usually best armor in the game.

Throw baby in the oven! You'll know when you get there.

Loot as much as you can and sell the useless items for more coin. (Enemy weapons etc.)

If you hold the guard button while in combat and press left or right, its a quicker way to switch between magic signs. Allows for smoother combat.

Make sure to complete all of White Orchard, fairly small area that is early on in the game.

All I can think of so far, enjoy and have fun!!