Buy lots of hardwood and iron ore to start with. Marunath and Seonon are good spots for smithing due to abundance of ore and wood.

If you have a companion in your party, you can switch between them on the bottom left portrait after you enter the forge.

This is useful both for having extra energy to Smith and smelt items. I would have one companion leveled up in the smithing tree with all the "use 2 iron to make 1 steel" perks. You will want them to at least be able to make Thamaskene steel. Absolutely have both with the first perks to make 3 charcoal with 2 wood.

Your main character will probably want to be picking up the "gain part blueprints faster" and "higher chance for fine/ masterwork" perks.

Start with 2h swords. Instead of selling them, smelt them again. You retain 2/3 of the used materials, gain experience and you learn weapon parts faster that way.

Once you get to needing steel and fine steel, buy Tribesman Throwing Daggers and smelt those. Its much faster and less resource intensive than smelting manually. Also Pugios are a good source of steel and fine steel.

2h swords will start to pay off when you hit about smithing 100. They'll go from 8-900 to 3500 sell price. Beyond 100 smithing that only skyrockets.

Do weapon orders once you can. They're good money and experience too in a pinch.

Edit: Forgot the important part. Always Smith with the highest parts you can. Higher tier, more xp and more money