I'd like to setup some network monitoring, but need some guidance.

I have a large physical area, but not a very advanced network. However we are getting more advanced, like adding VLANs and a branch in the not too distant future. Ideally I would like to create a "page" with a typographical layout of ISP > switches > switch node ect. Something at glance could help me see where issues are comming up.

Any suggestion on what would best allow me to monitor traffic and devices. Much of the network gear is merki, but some leftover netgear. For Pricing I like to stay away from recurring cost if at all possible. We are a nonprofit.