Are you looking for a mechanical mod or a regulated mod? If you want an affordable mechanical mod you should look into clones, hcigar and infinite make fairly nice clones in my experience. Also the doomsday mod, which is an authentic mechanical mod, is under 100 dollars and is very nice. If you are looking for a regulated device, I think an itaste MVP v2 would be an upgrade from your current setup, but if you are looking for something more powerful than an mvp v2, that is regulated, you could consider the Sigelei 30 Watt, which does go up to 30 watts, so you can go down to 0.5 (I think) and that is also under 100 dollars. However, for this mod, you would need to buy 18650 batteries and a battery charger which would add to the price. Overall, if you are looking to get into much more powerful mods for cheap, the only way in your budget in my opinion is to buy clones.