Wood is where most of the flavour will come from, so apple, oak, and such likes. My advice is to find maybe 3 wood types and explore those first, then build up your 'aromatic library' in your mind and see where you want to take it. I tend to have a few dishes as my benchmarkers for flavour testing, a pork shoulder chop, lamb neck and a chicken thigh boned out to a lollypop style (bone exposed like a handle).
The chicken I give a natural full-fat yoghurt marinade too, as it's a great way to trap flavour notes and often it helps the meat stay succulent and it protects it from burning (think tandoori chicken), then if left to cool overnight the flavour develops onwards. And often you'll know if the seasoning is correct when the food has been chilled and tasted cold from the fridge the next day.
For rec's on products, there are guys like Dan 'Smokin Elk' Whitaker and Kung Fu BBQ that are worth a follow Instagram, these people cook outdoors way more than me these days.
http://picbear.online/thesmokinelk