A really interesting 'Doctor X Tardis' fanfic I've come across is 'Tardis Tales'. In this fanfic, the Tardis has a sort of consciousness that the Doctor tries to fully understand. It delves into the mystery of the Tardis' inner workings and how it has a connection to the Doctor on a deeper level than just being a ship. It's a short but engaging read that will make you look at the Doctor - Tardis relationship in a new light.
Often, it involves exploring the unique bond and adventures between the human Tardis and the Doctor. There's a focus on how this unconventional setup changes their dynamic and the challenges they face together.
Good character development in both the Doctor and the Tardis is key. If a fanfic delves into the Doctor's past experiences with the Tardis and how it has shaped him, and at the same time shows the Tardis evolving in some way, it's bound to be great. For instance, the Tardis could develop new functions based on the Doctor's needs over time. Also, a vivid description of the Tardis' interior and how it feels to be inside it can really make a fanfic stand out.
It's a subjective matter, but some fans might rank the classic series' 'The Caves of Androzani' as one of the best, while the least favored could be 'Love & Monsters'.
I recommend "The City's Extraordinary Medical God" to you. The main character of this novel is called Ye Fan. He knows medicine and meets a pair of sisters on the way. The elder sister is sick and goes up the mountain to seek treatment from Ye Fan. I hope you like this fairy's recommendation. Muah ~😗