For me, I think generally around seven or eight. Ip try to go for a nightblade who HEAVILY uses magic to stay hidden, cause some damage, buff up and conjure.
Skills:
1-H (only invested a couple perks but I still rely heavily on stealth kills and when things get hairy)
Conjuration (LOVE IN THIS GAME but I try not to OP it)
Alteration (I like I just wish dragon hide lasted a little longer and alteration in general had more utility spells)
Destruction (no real problems here, I'm lvl 52 and still use chain lightning and fireball along with the wall)
Illusion (love using muffle n invis along with calm and frenzy, as lvl 51 I now have to cast master spells so they work, so just simply go invis n cast em)
Sneak (didn't need to invest many points as I use a sword and wear robes, but it's EASILY my most used skill)
Restoration (haven't used much but I like some of the spells and I'm getting to a point where I have perks and won't know what to do with them, soi thought I'd give this a shot)
Smithing (mainly to bring in money and I love crafting)
So I focus on around 7 skills with a possible 8th.
What do you guys specialize in? How many skills do you guys focus on? Post your builds and skills here I'm interested to see!
P.S. I know my build is funky but it's extremely fun and difficult. Definitely a glass cannon and worth it. It's very rewarding and not OP at all since I don't use enchanted weps, only some clothing. Only 150 health at level 52!