So i'm playing a Warrior, Light armour, one handed, shield, bows and restoration magic as backup and i want to do smithing and enchanting too.

Is that too many skills to level up?
How many skills should we concentrate on?

Your skills will be the strongest if you limit yourself to anywhere between 3 to 5 skills. Remember that the first perk in the tree usually has five steps, and if you only take the first one, you're missing on quite a lot of effectiveness. If you take more than 5 skills, you'll probably not reach the maximum of how strong each skill will be, but then again you become quite versatile. I don't know how much more difficult it will become if you spread out your skills.

I'm doing exactly the same as you, except I'm using heavy armor and haven't bothered with enchanting. I'm level 13 and have just got smithing to 30. I've put points into one-handed weapons to increase damage, a couple in restoration, one in block, one in heavy armor, and enough into smithing to unlock Dwarven armor. I can't imagine I'll be max level by the time I finish the main quest, so I've just got myself a few nice bonuses in some trees with one or two points and the rest I'm using to max out other trees. I don't think you can master of all trades in Skyrim.

Should your goal be to max out 2 or 3 skill trees you feel are your main skills and fill in the blanks with minor skills? How long are people holding on to perk upgrades before using them?

I'm using a total of 5 skills. Level 9 all of them are in their 30's. I think I'm doing well.