The Beginner's Guide to Artificial Intelligence in Unity

The exact details of a proper Mario Kart 64 level? Maybe a bit too challenging, but a simple racing game isn't exactly difficult when you look at Unity's built in car controller sample scripts/models. There's plenty of free car models on the store that are free too. (Some even look pretty decent.)

A racing game really only involves a tiny bit of logic outside of the car controller and AI. You need a collision box that counts the number of laps so you know when to trigger the end. Assign a script that checks each car's finishing time against the starting time and you can figure out who and in what order, the winners are. If you want AI cars, look into an a* AI course. Udemy has a good one done by Holistic3D that you can find here: https://www.udemy.com/course/artificial-intelligence-in-unity/ (Though you may be able to find enough free resources if you look hard enough.)

To create the levels you can find ProBuilder as an asset provided free inside Unity (find it under window>package manager, you'll need to install it). It'll let you build some blocky terrains very quickly. If you want to get more complicated you can look at BlenderGuru's free video tutorials to learn more about using Blender's free 3D modeling software.

Adding menus, making it look pretty, and tuning the challenge of each course will be difficult and time consuming, but getting working game mechanics you can play should only take a couple days at most. If you boil any game down far enough, most of the main mechanics can be emulated with minimal time and effort, it just won't look pretty. ;)

So in terms of courses (I'll try to provide all the free/cheap ones that are from reputable places) 

Coursera - AI for everyone - this is a pretty solid first place to start 6 hour course that's free and by the creator of coursera, and should give you some more ideas of where to go next/focus your learning as it's non technical and aimed as an overview of AI and it's possibilities

Coursera IBM - Applied AI - there are more 'official' coursera courses with certifications, there are quite a few, but industry sponsored ones are best imo. There's also Google certified ones on coursera and Amazon. There's ones from universities too as well as online masters delivered through coursera, but I think if you aren't wanting to do a masters then the industry certified courses are better for employability than the shorter university courses as the industry ones are much more applied and you will produce some of your own work as part of it. I find the none masters university coursera courses are more theory based/harder to practice. There's also a ton more free courses on coursera that it could be worth you doing before committing to pay as you might find you want to specialise in say machine learning and then a more specialise certificate course could be the way forward. I believe they also offer to cover funds for the paid industry certification courses if you're unemployed for the industry certified AI specialism courses, I think you have to apply with how it will help you and that you are committed etc. 

https://ai.google/education/ - google have a shit ton of free courses, guides etc. 

https://www.freecodecamp.org/learn/ - there's a ton of free learn to code resources, including game based learning etc. but I've found this is my favourite. They recommend you start with web coding languages, but I think for AI focus you could start with the 'scientific computing with python' if you really just want to get stuck in and then pick up tools such as visualisation later. 

There's also UK Government skills toolkit with links to various AI courses (all free) - https://theskillstoolkit.campaign.gov.uk/

and the Institute of Coding has a mix of courses and guidance too  - https://instituteofcoding.org/

There's also specific courses out there depending on what you're interested in with AI. E.g. there's a really well rated one for AI in gaming AI for gaming sector

Once you learn python then there's tons of cool online resources to practice and play around and learn and build stuff - e.g. https://gym.openai.com/ 

In terms of masters in person at UK universities then the government worked with higher ed to create a conversion masters for AI. I believe they have scholarships for people from underrepresented groups, else they can be really expensive. Here's more info. https://www.officeforstudents.org.uk/for-students