1. Enchanting, smithing, and alchemy are fantastic skills to use aside from your combat skills. Yeah it takes a bit more time collecting ingredients, soul gems, and ingots. But it makes you level up a lot faster that way.
I was level 28 in 4-5 days, and I am not even close to finishing the main quest line.
Also enchanting and smithing in combination makes you stupid strong especially if you have if you have a damage enhancing enchant.
I had 31% increase of my two handed blades on both my helmet and body armor. Every normal enemy goes down in one hit if I hit him strong.
Also I had smithing improvement increase on two of my equipment too.
2. Doing the first gets you a lot of items that you can sell, and it gets your speech up a lot faster.
3. Just do everything as much as you can, I use two handed most of the time but I also use my daedric sword to heal and use destruction magic.