I'd stick with the 9mm for sure.
The cheapest, good quality guns I would buy are:
used S&W 5903, 5943 (lighter aluminum frame version of 5906)
used S&W 6906
used S&W 3913
used S&W 5906, 5946
Ruger P95
Sig sp2022
Mid-range price:
Glock 17, 19, 26
XD 9 in any variant
M&P 9, 9c
Walther P99 (used)
used HK USP 9
There are more, but these are easy to find.
The cheapest, good quality guns I would buy are:
used S&W 5903, 5943 (lighter aluminum frame version of 5906)
used S&W 6906
used S&W 3913
used S&W 5906, 5946
Ruger P95
Sig sp2022
Mid-range price:
Glock 17, 19, 26
XD 9 in any variant
M&P 9, 9c
Walther P99 (used)
used HK USP 9
There are more, but these are easy to find.