Just read a few and clogged up my brain^ You're an encylcopedia!.

Do try the historicals: there's only four complete stories anyway (counting The Time Meddler, which still feels like one, despite the plot twist), two of which are at the top of the surviving Hartnells, and one immense fun (The Gunfighters is either rubbish or underrated, but either way, it's not a good one to try early, in case you loathe it and it puts you off historicals or Hartnell altogether).
Also, the whole historical/SF/Sf-historical division is a bit of a fanon thing: that's not the way it works in some of these stories. The Aztecs is arguably more serious SF than The Time Meddler, as it thinks more deeply about the SF issues of whether a time traveller can alter history.