No-one here can give you an answer based on your vague question.
The price is based on the size, weight and thickness.
Go to
www.royal-mail.com they have price guides, charts and calculators. Go via Google Chrome browser and use the translate feature if needed.
Prices usually rise in March/April so my choice would be the 1st stamps, assuming the value of those is enough for your item (each one is currently worth £0.63)
Re-using stamps is a huge risk fyi.