Below are a list of recommended plugins that I feel should be compulsory for any website.
A powerful SEO plugin.
Prevents spam and other malicious attacks to your website in an easy step by step form.
Advanced Custom Fields
An excellent plugin for creating custom fields. Works well with custom post types
WP Asset Manager
A plugin that deactivates individual or all wp plugin styles and scripts per page to increase load time.
You can also insert and disabled custom styles and scripts.
CMS Tree page View
Plugin that adds a CMS-like tree overview of all your pages, like the view often found in a page-focused CMS. This page tree gives you a great overview over all your pages and you can use the page tree to quickly drag-and-drop your pages to change their order.
Broken Link Checker
Detects broken links in your website and prompts you to fix them
Contact 7 form
Only use it as a last resort as you can only create basic forms. Any customisation will require a new build. Build your own and make sure it submits to the database.
WP Super Cache
A page caching tool. This should only be used for sites with very high traffic though using WP Asset Manager would greatly improve your page load.
Any gallery plugins
Your a developer, built it yourself. Using advanced custom fields is the best method, you can install an extension to create repeater fields.