Out of curiosity, will an extra years experience in certain fields/participation in charity work make myself an attractive applicant?
A strong personal statement, an excellent set of secondary school grades, and a GCSE C grade (or equivalent) in a language (if going into the humanities) are what will make you a more attractive candidate to Edinburgh. You'll also need a decent dash of luck.
Gap years are neither here nor there for most universities - unless you're applying for something like VetMed where the extra year allows you bank extra work experience and tick boxes. The biggest benefit to a gap year is that you have confirmed grades.