I have a gift for you buddy 
https://www.curseforge.com/wow/addons/bad-boy
https://www.curseforge.com/wow/addons/badboy_ccleaner
You need both, BadBoy is a spam blocker and the CCleaner extension lets you add custom text to block
Whatever you add here you won’t see in chat anymore so if you add:
for gold
You won’t see any messages containing that string. WTS M+10 carry for gold, WTS H CN for gold, starting in one hour pst, for example won’t show up in your chat.
Personally I just block
wts
wtb
wtt
w.t.t
w.t.s
w.t.b
w t t
w t s
w t b
because I don’t do player to player trading of any kind but that’s just me. You can use it how you see fit.