I'm not certain, but I think Hussie said somewhere that it is a possibility that Gamzee wanted to make a Bard costume because it would be funny. Putting fake wings on a real god-tier, with the real wings underneath? That's pretty funny, or at least I'm sure it would be in Gamzee's eyes.
But we've already seen him recieve the codpiece from Kurloz, and it's strongly implied that the rest of his attire was gathered this way.
To Meulin after recieving the codpiece:
EXCELLENT WORK, ďĽďĽą ďĽďĽˇďĽ§ďĽĄ
WITH THIS ďĽďĽŻďĽłďĽ´ RIGHTEOUS ďĽďĽŻďĽ´ďĽ¨ďĽĄďĽ˛ FUCKING PELVIC APPAREL, THE WICKED ENSEďĽďĽ˘ďĽ¬ďĽĄ IS NOW COďĽďĽ°ďĽ¬ďĽĄďĽ´ďĽĄ
and to Gamzee after giving it to him:
I COďĽďĽĄ BEARING THEE FINAL JOLLY ACCOUTREďĽďĽĄďĽ®ďĽ´ ďĽďĽą FAITHFUL INVERTEBROTHER
THY BARDLY REGALIA IS DONE AND FUCKING DUSTED BY THE SPECIAL STARS THEďĽďĽłďĽĄďĽ¬ďĽ¶ďĽĄďĽł
ON THIS DAY THE DARK CARNIVAL REJOICED AND SAID IT WAS ďĽďĽŻďĽ®ďĽĄďĽą
NOW BRING TO LIFE OUR WICKED RUSE WITH APLOďĽďĽ˘ ďĽďĽą NINJA
The word Ruse is especially telling, imo.