When you sign up for Internet service, your Internet Service Provider (ISP) will send you a consumer-grade router which often also functions as a wireless router. For most people, this device is "good enough" from a security perspective. But I would like to suggest investing in your own network equipment. This has several advantages.
Many ISPs charge a monthly "rental" fee for a router. While this charge may seem small, even $5 per month adds up to $120 over the course of 2 years. Having your own equipment may actually save money over the long term.
Having your own router gives you the flexibility to change internet service without having to reconfigure your internal network and can reduce "down time" if you change ISPs. If you use the router supplied by your ISP, if you get new internet service, you will have to install a new router. This means you'll have to set up a new router, configure the wireless settings (including your wireless network name and password), you may have to configure other network settings, such as how your router assigns IP addresses. You'll be doing this on an unfamiliar device, which may be technically challenging for some.
Conversely, if you have your own router/wireless router, when your new ISP sets up the service, all you simply have to do is unplug your router from your old ISP's modem and plug it in to your new ISP's modem.
The router that your ISP provides may not have some of the more advanced security features found in other routers you can purchase. Even something as simple has changing your Domain Name System (DNS) settings is often not possible with a stock router provided by your ISP (I have another post on why changing your DNS settings is important). But if you "BYOR" (bring your own router), you have full control over all of the various security settings. And you can even chose to purchase an even more advanced firewall, vs a standard router (more information about firewalls is here).
Bottom line, I strongly recommend you purchase your own router or wireless router!