Here is what I would do.
1) install/configure SNMP for all the systems (servers? Windows? Linux?) you want to monitor
2) if possible, obtain a list of IPs for the servers (DNS export?) and use SW discovery to import the nodes, but only get the top cpu and mem, the volumes and the non-loop back NICs. (if you have Server 2008+, you may get extra NICs that you have to sort through).
3) get used looking at the top 10 lists, seeing what is gathered.
4) setup alerts for high sustained CPU usage, exclude some nodes that have it and is normal, move to RAM, NIC usage, volume space remaining, etc. Wait till you are comfortable with that (maybe a month with just NPM features).
5) Consider getting APM and a list of applications that are important to your business, then map those applications to processes running on servers, network ports that are available, words on a web page, etc. and use APM to monitor them.
The important thing is to take it in steps, like you said, there is a lot you can do, don't try to do all of it at once. Make reasonable goals and it should start getting easier as you go.
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Welcome to the fold, sumfknguy!
Orion can be intimiadting but once you get an idea of what it can do and what you need to accomplish it is pretty cool. As mentioned you need to collect some basic information, turn on SNMP and then start playing.
Throw out questions as you go, no matter how simple and someone will respond - usually.
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Thanks!! Appreciate the welcome!