Incense in general I'd say is a big no - you get probably 5-6 Pokémon per incense compared to usually 10+ per lure. If you want to level up fast then Lucky Eggs are definitely worth buying and then save them for when you have a lot of Pokémon ready to evolve at once for tonnes of exp. If you want lots of Pokémon, go for Lure Modules and Pokéballs (seems like a waste but trust me you'll need more balls when you start buying lures - always keep enough coins for some spare balls just in case). Incense is fine if you don't live near any PokéStops but that's about it really, I wouldn't encourage buying that really ever if you want to spend the money wisely. Incubators can be good based on how close you live to a good number of PokéStops for egg spamming.Esper, I love that attitude. I messed up a couple times before I realized the optimal path, too.
I'm still trying to decide what the best use of actual money is for this game. I spent a little to upgrade my bag, but now I'm weighing... Lucky Eggs? Incense? Incubators?
I think Lucky Eggs wins out, but maybe I'm wrong.
Incense in general I'd say is a big no - you get probably 5-6 Pokémon per incense compared to usually 10+ per lure. If you want to level up fast then Lucky Eggs are definitely worth buying and then save them for when you have a lot of Pokémon ready to evolve at once for tonnes of exp. If you want lots of Pokémon, go for Lure Modules and Pokéballs (seems like a waste but trust me you'll need more balls when you start buying lures - always keep enough coins for some spare balls just in case). Incense is fine if you don't live near any PokéStops but that's about it really, I wouldn't encourage buying that really ever if you want to spend the money wisely. Incubators can be good based on how close you live to a good number of PokéStops for egg spamming.
https://www.serebii.net/pokemongo/trainer.shtml There's a list of items per level here - hopefully this helps! As for your question about the eggs you receive, as far as we know it's random with 10 KM being the least likely to get.I would never buy anything in this game, but does anyone know what levels give you incubators? I think I got 3 extras twice before level 13.