Product Testing Phase

Hi All!

I'm looking to test products via dropshipping to slowly build by brand. Before I do so I had a few questions:

1) For testing phase, do I need to build a relationship with sellers on AliExpress or does that come afterwards?

2) Do I need to create my own content by ordering sample products (i.e., shooting an ad for TikTok), or is this better once I see that my product is selling?

Any help would be appreciated!