lol 300 budget is easy
but finding good fullsizes isn't.
If you want one board: shine 3 with some nice PBT caps, or new deck keyboard with doubleshot backlits
What I would suggest tho:
Get a tkl and then a numpad. Same keys, two pieces, more options.
numpad--filco, leopold, etc, most are $50 tops
tkl: shine 3, deck, or go down the customs road. Grab a phantom PCB $32, plate $25, teensy $20 switches $50 non metal case $30 about $175 (and ask for shipping discount for buying multiple stuffs from mk.com) Total is $225, for a sweet setup that you can customize all you want