Trading Magic cards is like making money in this way: You have to HAVE money to make money/You have to HAVE tradable rares to get good/superior rares.
If you have to get superior rares for your trade binder, then why don't you just get the rares YOU need? Without an income that allows you to buy cards without thinking about it you're kind of caught between a rock and a hard place.
I HORDE my really tradeable rares because I'm usually USING them. I once had two Chrome Moxes. I decided that getting two more was not worth my time and effort so I put them in the old trade binder and got lots of stuff I really wanted/needed for them. It's in THOSE cases that I make the descision if I should want to keep a teir one rare or not.
In drafts, I also look for tradeable rares. This can only happen on picks one and maybe two for each pack. I opened this past Friday night in pack two a Darksteel Colossus. A playable card for my draft deck? No. but a hellava good trade binder cache.
I really wouldn't worry about having a "NICE" binder for right now. As a matter of fact, I see a lot of folks, especially young ones, put together a trade binder chalk full of broken rares only to really show it off as a "Look at MY rares" binder and then close the binder and skip the trade part. I HATE that. There are two kinds of binders that should not be mixed up: A trade binder, you know, stuff that you will actually TRADE and a "Showcase" binder, the Power Timmy one that you show what YOU have and what they DON'T have.
What was this about? I forgot.