Here's a few tips on how to start finding opportunities immediately:
Set some filters (category, keywords, etc)
Sort by listing creation date (usually the most recent Ebay listings are the best ones)
Start from the top of the feed. Go through every opportunity, and click the "Inspect" button.
Check to see if you can sell the item by clicking "can I sell?" If you can't sell the item because the brand is restricted, click "ban this brand from future searches" to prevent that brand's products from being shown in future searches.
If all is good, add it to the "saved" list or purchase the item immediately. If it's not good, either report the item as a mismatch or mark it as "seen."
Rinse and repeat! Finding good opportunities takes patience and persistence.