Lab-network Need 1000+ IP addresses on same subnet (DHCP) easiest way possible..

I have an AT&T Router (Uverse internet) and some switches, access to computer hardware, wiring etc. My issue is that I immediately ran out of IP's since the 192.1.x.x/255.255.255.0 network that the router leases from only allows 190 or so. How can I get 1000+ (500+ needed) on the same subnet with minimal effort (disregard throughput etc. )

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My 'idea' so far is to simply leave the router as default, and use a Netgear FVS318 ProSafe VPN Firewall and simply wire it to the router with 176.16.x.x / 255/255/252/0 network settings for the DHCP to hand out IP's to the rest of the lab. Seem reasonable?

Ideally I'd like to be able to cross access devices from the 192 network (router) to the 176 network but not sure if it's wise.

I believe this is the router if that changes anything?

https://www.newegg.com/Product/Product.aspx?Item=9SIAJ7W8HJ3141