So I have a bad habit of making my characters OP, even if I don't initially intend to. I try to max out my preferred skills even before I start doing quests or exploring. I'll find some way to farm for levels, exploit skill growth or train in something I don't use as much. This begins with Smithing, my absolute favorite skill and one I use for all my characters, and what I like the call the Great Dwemer Smithing Run. I'm sure others have done this but here's what I do:
1. First I'll get Smithing to 30 either by improving as much gear as I can find or training. Then I take Dwarven Smithing of course.
2. Get to level 14 so From-Deepest-Fathoms appears in Riften (although I may start at a higher level). Then complete Unfathomable Depths quest to get Ancient Knowledge. I will perform multiple raids on Avanchnzel to get all the smeltable metal out of there and store it in Breezehome.
3. Begin Lost to the Ages quest to get Aetherial Crown, raiding all related Dwemer ruins along the way. By now my Smithing is usually in the low to mid forties if I have been improving gear as I go.
4. Using the Aetherial Crown, I combine the Lover and Warrior stones, purchase a necessary amount of iron and smith the hell out of Dwarven Bows. By now I will have at least 400 Dwarven Metal Ingots. Even without taking resting perks, this gets my Smithing to near 80 or so.
5. Finish off Smithing by getting more DMIs from other ruins, usually Nchuand-zel.
Averaging at least a few hours gameplay a day, I can finish this process in just a couple of days (sometimes longer if I farm my armor skills or train in between smithing all those Dwarven Bows). Then I have them all to sell to pay for training in other skills (although I am a huge fan of that Dawnstar Khajiit chest for getting money and supplies).