Looking for help with improving an old network

Hi! So I'm an IT trainee and I've been tasked with optimizing the switch infrastructure at my firm, which is pretty old and chaotic.
Here is the basic switch setup across five floors, with the important servers being on the 12th floor and the switches being a combination of HP aruba 2530-8G/48G and various HP ProCurve models. The most important part of the project is to add redundancy to the network, if needed by getting new switches.

My question is, what's the best way to go about it, especially when I haven't had any real practical experience with this kind of thing yet? Are there any good online resources on the topic you could recommend?

Thanks in advance!