Hi,

You can find all the information that you need here: https://www.odoo.com/page/become-a-partner

As for which partnership is the best. These are your options:

 Ready Partners
The Ready membership level enables Partners to start and grow their Odoo competencies. They benefit from a comprehensive set of services including training, support and access to leads which allow them to build their business at their own pace.

Ready partners also have to follow a minimum of 1 official Odoo training session.

Silver partners
Partners which have qualified for the Silver Partner level are experienced in implementing Odooprojects. Silver partners enjoy enhanced benefits as well as access to additional resources to support the growth of their business with Odoo.

Silver partners also have to follow a minimum of 2 official Odoo training sessions.

Gold partners
Gold partners have a strategic relationship with Odoo. Odoo is at the core of their strategy. They have committed significant resources to develop and deploy Odoo solutions. They benefit from the highest visibility in the Odoo ecosystem.

Gold partners also have to follow a minimum number of Odoo training sessions.

Hope it helps