This auction is for 1,000 commons and uncommons. It will be split about 65% / 35% with an approximately equal share to each colour (multicolour and artifacts will likely take some portion also). No basic lands. They will be taken from a pool of the following sets (you will not receive cards from all the sets below)

147 Ultimate Masters

222 Battlebond

102 M2015

136 Conspiracy

258 Eternal Masters

267 Ixalan

165 Rivals of Ixalan

336 Dominaria

A certain amount will also be taken from the Mystery boosters which reprinted a lot of the most powerful commons and uncommons in the main slots - I will consider all these commons for the purposes of the 65/35 split. There myself a few from other sets of a similar age if I come across them.

There is very unlikely to be many if any duplicates as I try and avoid it - it is inevitable though that the same card might be in 2 sets and I inadvertently pick the same card from 2. I would say this is exceptionally rare and the "base line" for duplicates is 0.