About stats:

Most important are 18 dex for the AC and ranged attack bonus, I also recommend 18 str for carrying capacity and damage, 18 con so you can even reach 20 con including regeneration, 18 cha for better quest rewards and cheaper shop prices.
Int and wis are useless compared to this, having both 10 int and wis too requires a roll of 92 to avoid a lore penalty but other party members will have higher lore and casting the spell will identify everything, so even much lower rolls won't make a noteworthy difference. I'd go for a roll of at least 89 with 10 int and 7 wis for cosmetic reasons but even a roll of 78 is almost perfect.

I'd start with sling and add quarterstaff proficiency at level 6, but reverse order or dart for ranged (more attacks but use up more ammo and have lower range) or dagger for melee is also playable, just make sure to get proficient both in a melee and ranged.


About spells:

Pick the spells you want to cast, don't choose some you don't like just because someone tells you they could be powerful, the game won't become unwinable if you are missing some spells. The usefulness of spell picks also depends on your party composition, "haste" is essential but doesn't have to be picked if you have a bard or wizard in the party to cast it for example.

You learn 5 level 1 spells during the game so spending 1-2 picks for spells which do really help early but get useless later should yield a better gaming experience than spells which still work later but you won't need because you've another working one.
"Magic Missile" is an essential spell at higher levels but relatively weak at low levels, I'd pick it at level 3 or 5.
"Shield"(protective) and "Identify"(comfortable) are also useful spells during the whole game.
"Find familiar" adds hitpoints and a powerful ally. You cast it only once during the game but it will take about a third of the game until you find a scroll, "Sleep" is very powerful for a long part of the game, pick those spells early or not at all.
The essential spell at level 2 is "Mirror Image", the rest depends on your playing style.


About party members:

Pick whom you meet and like, it's not a good idea to make this decision before playing. If you don't know the game it will make you unhappy if things don't go as planned or the NPCs aren't as imagined and drive you towards walkthrough hugging and if you've finished the game before you can afford to play any combination for the challenge.