Here are a few free resources that are helpful for ensuring visual marketing materials are high quality and high performing.
Bookmark this page to easily reference the latest best practices for social media image sizes. I visit this page frequently and really appreciate the comprehensive yet succinct information they provide for each platform.
These websites are great resources for free, high quality photography:
Death to Stock sends monthly emails containing 20 free photos.
Adobe lightroom is my favorite way to quickly edit photos on my phone. I often use either the "profiles" or "presets" feature as a starting point, and then make a few additional manual adjustments if needed.