If you are starting out your collection, I would give this some consideration as it may save you a fortune!
Don't look on ebay for a 1956 farthing that may cost you £1.49 including P&P, why not try typing in job lot, or kilo, then in the side bar click on the coins & banknotes option, you can get 300 coins for £20, they won't all be different but you put the multiples back on ebay for 99p and use the money that raises to buy gap fillers for your collection.