Latona

As stated, you could start with the lvl 1 spell upto lvl 13 and then you could keep usin the lvl 13 spell if you have a fire staff and plenty of air runes ( or an air staff and plenty of fire runes) along with loads of mind runes. With it being a pure and you dont want defense levels, make sure that you dont train it on focus otherwise you would get defense exp as well. P2p would be better - but even training it on cows at the crafting guild on f2p then moving onto the hobgoblins across the other side of the river would be fine.

P2p does offer a lot more benefits for the smither than f2p. Selling steel bars is basically the only option for lower level smithers to make money from the smithing skill. The experience isn't great for it, but at least it doesn't cost you. P2p on the other hand can take those steel bars, turn them into cannonballs and make a profit - or they can make lower items like iron knives and smith them at breakeven cost, or making a profit. Not to mention the gold ores - I still remember Howdydee2003 and a few others all of us working gold ores before Jagex allowed people to change the gauntlets :P Smithing is a skill that will cost money unless you are prepared to put in a lot of work in supplying your own ores - especially on f2p... good luck on the skill though.