Translation:Where in this city can I buy ancient, ceremonial weapons?
Should we infer from this sentence that, when affixing two adjectival verbs (ie, a verb that, in English, corresponds to an adjective) to a noun in the context of a larger sentence, where -'ej is not a convenient option, one verb follows the noun (as usual) and the second is turned into a subordinate clause with -bogh?
So if I want to say "The young, clever Ferengi sells purple gagh?", do I say Doqbogh qagh SuD ngev'a' Qupbogh verengan val?
No, you should not infer that.
So far as we can tell, you can't add two verbs adjectivally to a noun. So you can't say nuHmey tIQ SeQ, qagh Doq SuD, or verengan Qup val.
There are a couple of ways to apply all these descriptors. The most common way in canon is to turn ALL of the states or qualities into relative clauses: tIQbogh nuHmey 'ej SeQbogh, Doqbogh qagh 'ej SuDbogh, and Qupbogh verengan 'ej valbogh.
(Notice that I put the subject after the first verb in each case, following the instructions of The Klingon Dictionary. The fact that these are relative clauses instead of complete sentences is irrelevant. We have examples of conjoined relative clauses in canon. However, it's also allowed that the subject come at the end of all the clauses: tIQbogh 'ej SeQbogh nuHmey; Doqbogh 'ej SuDbogh qagh; Qupbogh 'ej valbogh verengan.)
You can also choose to do what this sentence does: pick one verb to act adjectivally and make the other(s) a relative clause. I'm not sure if we have any examples of this in canon (we might), but there's no reason it can't be done. However, it does seem to give a stronger relationship between the noun and adjectival verb than between the noun and relative clause. Qupbogh verengan val seems to be saying that here's a clever Ferengi, oh, and he happens to be young. valbogh verengan Qup seems to say that here's a young Ferengi, oh, and he happens to be clever.