There were some confusing bits, but overall this was a decent finale. The whole idea of the Doctor being in three places at once was a little crazy, and when there were two of her in the same place I found myself thinking of Austin Powers.
I was sad that Dan and his boss didn't work out, but maybe she will appear again.
As for some of the loose threads, I like the fan theory that Vinder and Diane (was that their names?) are the Doctor's birth parents, and I'm sure they will appear again, and that we'll find out more about Karvanista's relationship with the Doctor - it seems that he was a companion of Jo Martin's Fugitive Doctor (she needs to appear again soon).
That watch will come back again, almost certainly, AND the Grand Serpent.
As for the conversation with Time, the mention of a "master" can only mean one character reappearing; it's about time The Master came back, as well.
Now, I've posted the obligatory poll to see which episode this series was everyones' favourite (and least favourite).
Poll Favourite Episode of Doctor Who Series 13
Poll Least Favourite Episode of Doctor Who Series 13