DOS2 is NOT the kind of game that holds your hand. I can imagine new players are having a rough time getting started so I will try to give some basic tips that should help.
1) Take along a bedroll.
Healing potions and spells are a sparse commodity in this game, especially in the beginning. Sure you can rest in beds but sometimes you find yourself for away from any civilization. Luckily you can find a bedroll on the ship towards Fort Joy. Make sure to pick one up and keep it in your inventory. The bedroll allows you to rest between battles and will heal your party completely.
2) The ALT key reveals all the things you can pick up.
There is a lot of loot just lying around everywhere but sometimes its not that easy to see. If you press ALT all will be revealed! Mind you, you will still have to open crates and such before you can see what's inside. Be sure to look out for valuables like gold, silver or even paintings. You will be glad you have a lot of junk to sell when you want to buy stuff from a vendor.
3) Know when to run away and use your sneak skill
Sometimes it is wise to know when you are outclassed. Even enemies that are just one level higher then you decimate your party in minutes. Be careful when exploring and use your sneak skill (press C) to avoid getting seen.
4) Use the environment to your advantage.
More often then not battles will seem overwhelming. Always look out for ways to use the environment to your advantage. You can electrify water or blood and stun enemies. You stack crates to create temporary barriers. Also make sure you place your ranged fighters on the high ground. And avoid placing your guys near oil barrels or in toxic fumes.
5) Don't be a jack of all trades.
When leveling your characters makes sure you plan ahead. You will not get a lot of points to spend on skills and attributes so spend them wisely. A character that has one point in everything is not that useful. Play into the strengths of the character and make a diverse crew.
6) Quick save is your friend!
Auto saves are kinda sparse in this game. Make sure you save after everything important you do to avoid having to replay large sections.
7) Be prepared to die a lot.
You will die a lot in this game. Some battles may seem impossible and it's easy to feel overwhelmed. Just remember that unless you are facing enemies that are a higher level then you there is always a way to win a fight. Maybe you can lure the enemies in a better spot or maybe you can use your spells to better effect...
I'm sure there are loads more tips that can help new players so feel free to add your nuggets of wisdom below!