Optimizing my iMac

Hello!

I have a iMac (21.5-inch, Mid 2014) and I'm in school for coding and billing. How do I go about adding an addition monitor

I recommend external displays from LG.

LG Monitors

Your Mac will support up to a 30-inch external display that's 2560 by 1600 pixels. Additionally, chances are, the external display you'll choose will have HDMI connectivity, so you'll need a Mini DisplayPort to HDMI adapter to connect the display with your Mac:

Belkin 4K Mini DisplayPort to HDMI Adapter - Apple

enhance my Mac performance to handle the job

To see what specifications your Mac has, and what may be causing poor performance, I believe we need to proceed with an EtreCheck report. EtreCheck is a useful App to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.

2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities.

3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.

4. Run the report, and put it in a post, as shown here: How to use the Add Text Feature When Post… - Apple Community.We will then examine the report for issues in your Mac

Jack

Before doing ANYTHING, find out from the school if the coding they teach can be done on a Mac. My son majored in computer engineering and for the first few years he could use Terminal for the coding. At some point, the courses required coding software that only ran on Windows computers.

One man's opinion: I would not invest in that computer. The Mid 2014 21.5-inch was one of the crippled educational/institutional model with a dreadfully slow dual-core 1.4ghz laptop-class processor. The equivalent consumer iMac of the time, the late 2013 21.5-inch, had a four-core 2.7Ghz desktop-class processor as base CPU and it blew the socks off the Mid 2014. Benchmarks from the MacTracker database:

Upgrading RAM and faster internal storage cannot realistically be added at home, and the pro labor costs are expensive. And you still have that pokey processor.

You can throw a lot of money at the computer and it will still be slow.