go to a local shop where its usually nice selection and you can see em up close. 30$ should get you a typical, 8-14 inch acrylic bong with metal bowl. seriously, splurge a bit and spend at least 50 or 60 to get a 12" minimun glass bong that will outlast you.
my friend bought a glass bong for 10 bucks... needless to say it was the most poopy ass bong i have ever smoked out of. it was about 7 inches tall, and had a tiny rush that didnt even clear out the smoke. it was just a terrible piece. he sold it for 25 though haha
If you're looking for glass you're gonna get shit for $30. If you don't have a problem with plastic then you shouldn't have a problem finding one at a headshop that will work just fine.
I got a nice small glass on glass 3mm thick glass bong for 25$ at my local heashop.. You just gotta shop around...
I got a nice 12" soft galss bong for $25 at my head shop. just shop around, and dot buy something that is too cheap and will break or hits like shit, otherwise what the point of buying.