have purchased 365 business basic, don't have the right account so i can't access the software

Typically, you should be able to access https://admin.microsoft.com using the e-mail you specified during the purchase, and then you set up (custom) mail accounts.

Note that a 365 Business Basic subscription won't let you install the full versions of Office apps on a PC or Mac, though. You get additional online storage and custom e-mail addresses.

for some reason microsoft 365 admin. centre won't accept my gmail login ,

To resolve your issue with accessing Microsoft 365 Business Basic, you need to ensure that you have the correct account set up. Since you currently have a personal Microsoft account, you will need to create a Business account linked to your Business Basic subscription. Here are the steps to follow:

1. Create a Business Account: You need to set up a new account that corresponds to your Business Basic purchase. This can typically be done through the Microsoft 365 admin center.
2. Check License Assignment: If you are part of a work or school organization, ensure that your account has the appropriate licenses assigned. You may need to contact your Microsoft 365 administrator for assistance with this.
3. Use Online Apps: If you have Microsoft 365 for Business Basic, you can access Microsoft 365 Online apps until your account is fully set up.

If you encounter further difficulties, consider reaching out to Microsoft support for additional help.