Cheap V-Bucks

Best bet is to get the fortnite crew, £10 get 1000 vbucks monthly, the full battle pass, which means they can earn up to 1500 more vbucks that month

Best bet is a good deal on an Xbox gift card then redeem that on your account. More bang for your ‘v buck’ this is how I do it for my son. CD Keys usually have a small saving on any Xbox gift card

Unfortunately as far as I'm aware it's not so easy to get cheap V Bucks. You could potentially buy a discounted PS store credit code from a website such as Shopto, and then purchase the highest quantity pack. Whenever a new season starts they usually put a cheap £3ish pack in the store which gives an outfit and 600 V Bucks. Completing the Battle Pass to lvl 100 will give you more V Bucks than it initially cost, so if you can avoid buying anything, you can always maintain that without spending more.

Not necessarily the cheapest, but there are also physical packs you can buy in shops which will give you an outfit bundle as well as V Bucks. I remember a couple of years ago the Minty Bundle went on offer for about £10 in Asda which gave you 1000 V Bucks and 3 outfits.

If no VPN, then Xbox via Hungary.
1000 will cost around £6.12 instead of £6.99. No big savings but always something.

Everything else will be either: VPN or scam or stolen stuff that can get you banned eventually.

You can buy v bucks on turkish epic games account and gift items to your main account