As a generalization re: Gilberto Gil and Caetano Veloso, their greatest hits or best of compilations are not the way to go. I own about 20 albums from each including a best of from each. The song selections on the best ofs tend to based more on song rights than quality. In fact, I'd rank the best ofs that I own for them near the bottom of what I have. I'd also point out for Caetano, his earliest stuff is overrated based on its cultural importance. In terms of songwriting and musicianship, he peaked in the early 70's.
Tom Ze
I'm not nearly the fan of Ze that you and Tony are. As a result, I don't really listen to him that often and am not as comfortable ranking him. If I had to pick a couple best though, it would be Todos Os Olhos and Estudiando O Samba. "COM DEFEITO DE FABRICAÇÃO" which you've mentioned looking for was reissued by Luaka Bop this year so you may have more luck finding it.
Caetano Veloso
Transa is not only my favorite Veloso album...its my favorite album period. Next best (read my next favorite) but more mellow are Bicho and Cinema Transcendental.
Gilberto Gil
Gilberto is a more talented musician than Caetano but his work is all over the place and is not nearly as consistent. My favorites in rough order are Expresso 2222, S/T 1971, S/T 1969, Refazenda, Refavela. I list more because the S/T ones are pretty pricey. I'd guess you'd like him more than you think.
Cesaria Evora
Miss Perfumado is her best and a real classic. Sao Vicente is probably my second favorite. I haven't heard one I don't like yet though and many are available through Columbia House and BMG
Timbalada
Another band that can do no wrong by me. I'd say the self-titled debut is probably their best, and Pense Minha Cor is probably the second best but I have every album and they are all good. Weakest is probably Timbalada Dance which is remixes of songs off of other albums.
Edit: If you like Livros, Carlinhos Brown - founder and chief songwriter of Timbalada contributed the percussion on that album.
Cafe Tacuba
I only own two Cafe Tacuba albums, Tiempo Transcurrido and Cuatro Caminos. I like, not love both. Tiempo Transcurrido is a compilation and I'd recommend it above Cuatro Caminos but I'd recommend a lot of bands over Cafe Tacuba.
Gal Costa
She's another artist who is a bit inconsistent. I like her S/T 1968 album alot but its the only one that I've heard that I'd really highly recommend. Her S/T 1969 album and "Legal" are also supposed to be good but I haven't heard them. The S/T 1969 one can be a bit hard to find too although Dustygroove does have it in stock now.
I'd put Doris Monteiro high above her though in terms of Brazilian female artists.
Les Orme
I can't help you at all here. Never heard him.
I'd be pretty surprised if you wouldn't also really like Lo Borges and Marcos Valle. Marcos Valle is one of my favorites and put out a great string of Baroque Pop albums in the early 70's. They are out of print but if you can find them, get them. Lo Borges has a pretty distinctive beatlesque feel to some of his work.
If you're ever looking to sample some brazilian albums,
this site has a lot of streamable samples.
Also check your pm in a little bit.
np: Mandrill "Fencewalk"