There is three major factor to consider :
(1)-Your build :
How much PS/PD/PT do you have, and how much wpf for the weapon type.
If you exceed 6 for less than 80 wpf or 7 for 111 per example, your weapon will breaks really often (maybe almost double cost compare to a balanced build 6ps/140wpf).
(2)-Your armor(+horse) cost :
How much golds in this, it shouldn't exceed 20K.
(3)-Your weapons cost :
How much multiplied by (1) => if you get a good power/wpf ratio your can get a higher tier weapon without losing much golds with it. Otherwise try to use a cheap but effective one.
Cheap weapons:
Polearms : Long Bardiche (really good), Long Axe (faster), Long Spear (good utility)
2H : Morningstar, Longsword, Bar mace, etc ...
1H : I dont know much 1hs, but i know the Iberian Mace is op for it's cost.
And remember, it is not because you have a higher cost gears that you will succeed. Unless you are a heavy cavalry and you can spend over 60k on it (fuck these guys
)