[Columbine]

Ok, so the basic sentence "I give Mr Davies a T-shirt" I take it you understand?

私がダビスさんにTシャツをあげる

"I am going to~" is expressed using Vる+つもりです

So: 私がダビスさんにTシャツをあげるつもりです. I'm going to assume you've covered this bit already too.

The problem you're having is with the noun modifying, right? Ie. Modifying "T-shirt" with "Superdry", "buy" and from Ginza". You're right. You need "no" to make it "Superdry T-shirt" so スパドライのTシャツ. "From Ginza" is expressed using から, and then 'buy' needs to be in the past tense to make it "A shirt bought from Ginza": 銀座から買った

Put it all together:
私がダビスさんに銀座から買ったスパドライのTシャツ� �あげるつもりです。
Literally: "I am to Mr Davies a superdry shirt bought from Ginza the act of giving, am planning."
That's probably the most basic way of putting it. It's pretty text-book, so if you want it to sound more natural you'd need to play around with it.

EDIT: Theres some glitch diamonds, so you may need to hit the "quote" button to read everything. >/