As important as a single build can feel , I believe any combination of Riftmaker and Rabadon is gonna give you what you are looking for. The main problem with Smolder is the early game. It is SO easy to get swamped by enemies before you hit your 125 mark, so this build aims to negate that problem. Start with a Doran's Ring and build from there, preferably starting with Riftmaker. It'll give you the fighting power you need to be relevant and will allow you enough mana to poke with your W and deal important amounts of damage. I usually upgrade Q all the way and then W, but I have yet to try out maxing W for that early on extra dmg. Feel free to go for it.

It's important to remember that even though this build aims to cover the early game flaws of the champion while keeping that late game dmg we all like, early is still a problematic time. Try to focus on lasthitting minions with q and save your W to gain stacks on enemies while wearing them down. W is also great to stop ganks since it slows quite sustantiously, so keep that in mind if you are getting perma-ganked and remember to ward as much as you can.

Your E is definitely an ability you wanna save to escape engages. Dont engage yourself with it unless you see it incredibly necessary to secure a kill. Remember you cannot autoattack while casting your E but that you can cast your other abilities while in it.

You will be around minute 15-20 in average by the time you hit this mark. I know it might sound boring, but keep farming and stacking the passive. You can get more agressive on the usage of your W to level up your stacks as quick as possible. Hitting 225 stacks is key, as it unlocks the full potential of Smolder. So this is what you will aim for most importantly.