Ideally, the best seats are mid-field, between both 40 yard lines, and on the Club/Loge levels, 200 and 300 sections.
I find the Plaza level to be too low unless you're at the upper end. You're closer to the field but you don't see "the big picture" as well, which is why I like the 200/300 levels better.
Above that you start getting too far away from the action and at the 500/600 levels you get nose bleeds.
I don't like end zone seats because you can really only see what happens on your end, especially on the Plaza level.
Finding mid-field seats will be difficult and you'll pay out the ass for them.
Look at the seating charts and decide for yourself.
http://prod.static.saints.clubs.nfl....ket-Prices.pdf