Depends on how cheap you want to go with it but you can find both the sigelei 100w and ipv3 150w for around 100 bucks and with the sigelei you can build down to .15 and with the ipv you can build down to .1 so both are viable unless you wanna go super cheap and just get an unregulated box like the tesla invader which is around I think 25 bucks or so...