Anything less than 36x18x18 is difficult to maintain the correct temperature gradients. Even a small baby must have correct temps and every time you upgrade, your beardie is going to go thru stress adapting to new tank so best to get the size you want to have when full grown which is only a year old. Even better to get a 4x2x2 if possible.
Also, many of those kits include items you shouldn't use for beardies and don't include must have items. Example of items not good for beardies: coil uvb, repti-sand or calci-sand, red or colored lights, analog gauges aren't accurate, reptile carpet (can't be disinfected), freeze dried insects (no nutrition). Example of needed/safe items: T5 or T10 tube uvb 1/2 to 2/3 length of tank, white heat bulb for basking, temperature gun, topsoil/play sand mix for loose substrate or non-adhesive shelf liner/tile/paper towels for sanitary cleanup, live bugs of $50+ a month for 1st year for 2-3 feedings/day, daily fresh greens/veggies. After 1 yr old, a few live bugs 2-3x/wk (much cheaper) and daily fresh greens/veggies.
Pet stores are notorious for giving bad husbandry advice...they are usually young clerks hired to just sell stuff. Hope this helps.