There is no need to spend a fortune to start collecting. Some World War I medals, for example, can cost as little as £10. Even those costing £300-£400 may represent good value and there will be many between these prices. Medals, like coins, can be bought in groups which may provide interesting surprises, even if they are not especially valuable.
Underpinning your success, peace of mind and enjoyment will be your own research. Before buying, find out as much as possible about what you are about to pay for. The more third party information you can match to what’s on offer, the more you will be able to decide whether it is a fair price.
Useful online resources include the Forces War Records and The Orders and Medals Research Society.
Two important books in this field are Collecting Medals and Decorations, by Alec A Purves, and Medals: The Researcher’s Guide, by William Spencer.
For specific guidance on values and valuation, an important reference is the Medal Yearbook, from Token Publishing.
For commemorative medals a good place to start your research is the Royal Mint website.