Ultimately, your UI choices are yours to make and nobody can judge the complete mess you made of your screen. That said, there are some very useful PvP-addons that may help you perform better. This list shows the most important ones found on ESOUI:
This addon is intended for switching between builds, similarly to the Armory Station in the game. Unlike the latter though, Dressing Room supports an unlimited amount of builds to switch between, but this only includes gear and skills. If you also want something similar for Champion Points, seperate addons like Dynamic CP are available.
Imperial City Hunter
Combat Metrics is another addon to track PvP stats, but this time it is about damage, healing and more. There is a live window that tracks the damage you dealt and the healing your recieved, which is great for testing out different builds or if you simply want to be able to track how hard your skills or proc sets hit. On top of that, you can summarize these stats in a report window that shows for instance which source provides the most healing during a fight, how much your abilities crit and what skills hit the hardest.
Miat's Tick Tracker
This simply adds a small timer bar that shows when exactly your stamina or magicka recovery ticks. This happens every two seconds, so knowing when exactly the next tick is allows you to minmax your recovery. This can be done for instance by not blocking or sprinting right when your stamina recovery ticks. Note that you have to lock the bar in settings before the timer is visible.
Miat's PvP Alerts
Yet another addon to display PvP statistics, this one focuses on the situation you are fighting in. For instance, it displays how many enemies (including those in stealth) are around you and how far your allies or enemies have progressed in taking a keep or resource. The addon has more functionalities, such as a kill feed, distance to near forward camps, player lists and sound notifications.
Shadow Image Range
If you play a Nightblade, this addon is a good way to track how far away you are from your Shadow Image, in which direction it is located and how much time is left before it runs out.
This addon and others like it automatically replenish your weapon enchantment and repair your gear. Great timesaver and prevents you from running with a depleted weapon enchantment.