I am using a Canon 80D with an 100mm EF macro lens with 1:1, it's thread size is 58mm. I am looking to take better macro shots with more realistic lighting and to be able to take pictures in darker situations but I also like portrait photography so I am unsure which one to get, I would like some recommendations of which ones to buy, my budget is about £200-300 for either one.
I think for now you should save your money so you don't end up spending it twice. A ring flash can be had in your price range, but you are not likely to keep using it for very long. Bercause a ring flash will not get you more realistic lighting, it will do the opposite. It will wipe out shadows and create a very flat image.
For more general use, a Canon 580 II can be had used within your price range if you shop on ebay. Since you're talking £ not $, you might see what your local shops have. I haven't been in the UK in many years, but Jessops used to carry some used stuff as I recall. Does pixmania still ship to the UK? Their prices tend to be very aggressive.
I shoot portraits and macro myself and a flashgun will offer greater flexibility than a macro ring. For portraits, a flashgun can be swivelled so you can bounce the light off other surfaces, which creates a far more flattering and natural look than firing light directly at your subject. If you can't bounce the light then consider buying a bounce card such as a Rogue Flashbender.
With your budget, I'd get a Speedlight 430EX. I don't understand why other lenses and camera bodies are being suggested; what you have is very good and perfectly suited to your type of shooting.
Take a look at Wex Photographic; they sell new and second-hand kit.