I find the easiest way to up your smithing is to simply make your way through each of the major holds main city and visiting the smithery at each location. At first buy as much leather as you can and as much leather strips as you can and use the tanning rack to make more leather strips. Once you have about 100 / 200 you shouldn't need to get any more for a while. Don't bother buying ores from the smiths, just focus on the actual iron ingots. Getting ores just sidetracks you a bit as you've to find a smelter to use them and not every location has a smelter.
For example, today I started at Riften and bought out all the iron ingots and leather pieces that the smith had. I got roughly 25 ingots and 80 leather strips (after refining the leather) I made 25 iron daggers there on the spot and sold them immediately as they take up a lot of space in your inventory. I know I could enchant them and sell them for a much higher price but I was out of soul gems

I then made my way to falkreath and visited the smith there and hit jackpot. He had 47 iron ingots! Again I made 47 iron daggers on the spot, sold them and moved on. I skipped Markath as to my knowledge there isn't a dedicated smithery there that's easily accessible (as in outdoors) and moved to Whiterun. Here I got ingots and some more leather from both clerks at Warmaidens, the smithery to your right as you enter, and made my way to the skyforge. I bought all the ingots there and made roughly 80 daggers. I stopped then as I hat hit level 100 but if I was to continue I'd go to Solitude, then Windhelm and start again from Riften
By the time you hit around level 80 or so it will take about 10 daggers to increase your skill. It will take about 130 to get you from level 90 to 100.