setting up multiple IPs (networking novice)

Okay hold it. Yeah your speaking in VERY broad terms. A quick analysis is your not identifying the basics here.

First, complete forget about IPs and what the ISP gave you. Let's start with the 'basics' on WHAT IS YOUR GOAL?

So when you say "dozens of clients will be connected' are you talking a simple office building floor? Or you talking a large gaping open campus area? Are we talking some little Pub trying to be the next Starbucks or you talking you and your BUDS in your Dorm room all wanting to connect?

Really we need some idea what your intention is, then fully the area of impact, what are the assets to connect and WHERE determines HOW you connect. IP Management is THE LAST THING to consider in the schema if you don't even specify "oh I want wireless to that room 300 feet away on the other side of that brick and steel Dorm wall" .

That said, if this IS for a business your BEST solution would be to hire a Business Analyst to help SCOPE and DEFINE the project then provide projected costs and impact with a RISK analysis (what if one of those people is using your services to host Child Porn, YOU and your Buddy would be both LIABLE and CRIMINALLY implicated as "Child Porn' pedos and most of all first to be arrested!) then look to get some estimates for you. Normally some local "IT companies" and quite a few ISPs do that while thing for you, offering different terms and options (do you want to cut costs and lease the equipment since your first starting with a option to buy at the end of a specific time period? or do you want the outright costs to buying it all and the ABSOLUTE DEMAND to hire someone competent to maintain it).

Business class is NOT like your consumer plug in and use your used to. There are Firewall rules that need managing (you do want people able to look up about Breast Cancer right? But you dont' want them streaming Big Bazooka Sluts on their screens and leave you liable for 'sexual harassment' lawsiuts right? Don't believe me, people sue for all sorts even HOT COFFEE from McDonalds...remember!), then there is the actual setup of equipment and tweaking, not only IP configurations but what type of hardware will connect? Will it all be the latest hardware (802.11AC) or BYOD which may be legacy (802.11G) cell phones and laptops or tablets? That impacts the network as much as anything else?

So on and so forth. You need a full business analysis of what your doing, why your doing, how to do it, costs, and risks for doing it, before actually doing it... unless as I mentioned Harvey the Pedo next door leeches off your network and suddenly you have the FBI busting down your door for Child Porn

http://www.huffingtonpost.com/2011/04/24/unsecured-wifi-child-pornography-innocent_n_852996.html