If you just want some decent looking cards then Gallery is okay. They will not have much in way of parallels. They have some, but you may only get 2-3 in a hobby box.
As far as parallels and autos, if you are looking to be cheap, then your best bet is a panini product. Something like Mosaic, Prizm or Optic is usually fairly cheap and you will get a good amount of parallels out of it. Just understand value wise, it will be a losing venture, but if you just want cards to collect and never really trade or sell, then this isn’t bad.
Flagship will get you a decent amount of parallels and an HTA box will guarantee one auto. Those aren’t horrible price wise.
Archives gives a decent amount of parallels in a box and should yield an auto. Those aren’t too badly priced either.
If you really just want parallels and are on a tight budget, then buying singles is what will get you the most. You could spend $250-300 on a HTA box and get one auto and probably 8 or so parallels. Or you could spend $250 and buy some single parallels and end up with 200+ parallels depending on the players you wanted.
Right now at many walmarts you can get allen & Ginter blasters and Gallery blasters from 22 for 17 bucks a pop. Id try one of those although odds are somewhat long.
If you have enough money for a hobby box, check with Blowout or Dave and Adams or Steel city collectables for hobby boxes on the cheap. Some 2021 heritage hobby boxes were selling for 50 bucks! Guaranteed a gu or auto per box.