in your hurry to buy, be aware of many sellers who may scam you.
first, check if they provide original email accounts. with the email account provided, check to see if the very first email from instagram is there, the one that's sent to you by instagram when they first create the account. it will have an activation link.
without that original email, you won't be able to retrieve your IG account if it's banned or hacked.
next, ask for one or two free accounts to try out first before you buy in bulk.