You should wear what you're selling for better advertisement
You should wear what you're selling for better advertisement =売っている物を着ていた方がいい宣伝になるよ
advertisement =宣伝、広告
少し優しめな言い方を提案してみました。ちょっとおちょくりたいのであれば:
Really? Where's your suit? =本当に？あなたのスーツはどこ(にあるの)？
って言っちゃいましょう。確かに信憑性ないですもんね(笑)。
You're a moving advertisement, so why don't you put on your product and call out to people?
You're like a moving ad, so how about calling out to people while wearing your own product?
「ad」= advertisement
「put on 」と「wear」の違い、わかりますか？
着てから外に行く... put (the clothes) on, and then go outside
着ながら声かける... call out to people while wearing (the clothes)
アメリカ合衆国 
