The latest series (7) is kind of middle of the road in terms of style, so maybe it's a good place to start? Asylum of the Daleks, not the preceding Christmas episode, it is not good
The stagey aesthetic of the classic series can be weird at first, so it should be easier to get into with the newer episodes. Also "season
" means 1963-1989 (or all) while "series
" is 2005 onwards. Series 5 might be a bit closer to classic series though.
Series 1 has its own weird sub-style so it might be less representative, even if all seasons have a bit of their own style, that is one of the more peculiar ones.