I am 52 and haven't completed the main quest yet. I just play the game and level combat skills. Ever since finishing the Companions questline, I use the free training points every level (I am currently training 5 points of 2H every level just for the advancement, even though I have no plans to ever use one)
I have 1H, Heavy Armor and Block all to 100. Even though I can just melee through a dungeon, I have always used Sneak and Archery when exploring and switched to melee when the enemy closed. I have Sneak at 100 and Archery in the high 80s I think. The only magic I use is Restoration which is at 51. The only other magic increases I have gotten are the occasional book find and maybe 3 or 4 points in Alteration from Transmuting Ore.
I now have Smithing to 85 and Enchanting to 70, but I didn't "power level" them. I didn't want to do either of them early on really as I didn't want to be underpowered in combat. I just saved up ore and hides as I found them and did a little Smithing here and there from time to time for some increases. Enchanting I got to about 50 just from disenchanting stuff and recharging weapons. I finally took a whole bunch of jewelry (I never sell any of it - I have at least 60k worth in an end table in Breezehome) and raised it from 50 to 70 enchanting a WHOLE bunch of rings with waterbreathing (only uses petty gems).
The main thing is I just played. I went out and fought stuff, got skill increases and leveled. I saved all the pertinent loot for 40 something levels (ore, hides, jewels) and then worked on Smithing and Enchanting much later. I have only dabbled in Alchemy, probably 30 something skill atm, but I have a TON of alchemy ingredients and can probably level that pretty easily whenever I feel like doing it for an hour. I never sell any of those either. I save every single one I have ever found.
I really only want/need 6 or 7 more levels to get the Alchemy and Enchanting perks I still want, and then I am done as far as character advancement.