1. golden charms - how many of them (average) is it possible to gather (find, buy) during one game? (until wastelands i found only one...) - i have some items not charmed yet (i.e. 5-slot helm of the dragon) - and wonder if to stuff it with silver or wait for golden...
You can buy them in the Wlands from Kroxy--as many as u want.
2. skill books - i managed to buy/find some of them (about 15) - but all of them were way of the mage skills (i play as a survivor) - is it possible to find/buy survivor or warrior skills books?
Only mage books. Some equipment comes with survivor or warrior skills on it as u no doubt already know.
3. i specialize in ranged attacks (elemental arrows rocks...) - i was given bow of hifin as a reward for a quest... is there a better bow in the game?
It is the only unique bow. You can find or buy a bow you might like better particularly at the elven village, but you never know. I don't know about the bows in the wlands for sale--I already had a bow I liked and stopped paying att'n to the stats on bows for sale.
4. i noticed that items in dd give a huge boost to stats (especially health and mana...) - and i think that only agility deserves putting points in... strenght only to be able to wear a decent armor - constitution and intelligence - few or no points... for now this strategy works fine (i'm playing normal difficulty and don't have to buy potions at all) - i wonder if the game will turn more difficult in the wastelands?
No it will not get harder except for Josephine. Imo once u get your offense to 94% & defense to 19% you don't need any more points in agility--check offense & defense every time you lvl up and assign stat pts. Strength boosts your dmg and how much u can carry. Intel is probably useless (AMD is better anyway.) If u have a skill that is heavy on mana then put a gold charm in later for mana. Constitution? Can't hurt.
Welcome to the forum. Enjoy.