before spending any money, just reuse old equipment you have around, even if it wont max out the speed. You can try out openwrt, opnsense, openbsd, linux, etc... deciding which ecosystem you like is very important before you buy hardware!!!! Different devices have different hardware support, etc.
Regarding hardware - Your fiber connection is 5GiB but your ISP cpe only has 2.5GbE ports, so you will need to bond two ports together to get your 5GiB throughput to your router. Once you select your routing environment, you can choose hardware that allows for multiple wan side ports that you can bond. (Perhaps your ISP has a CPE you can get 10GbE out of, or with a spf port, the same for your router)
Regarding Switches - You don't need a fancy managed switch, as long as you trust devices on your network to do peaceful vlaning on their own, you can just send vlan tagged traffic across a dumb switch no problem. Only when you start talking about doing default vlan tagging and enforcement on a per port basis do you need a fancier switch. So depending on what you want to do with vlans, you can save money here.
Regarding Wifi - Depending on your routing solution, it could have wifi attached to it, or you can just get a specific access point on your network that only provides wifi and rely on your router/gateway setup to do all the configuration.
FWIW - I just go full ubiquity, router, switches, ap. I used to fiddle around with openbsd routing, and it was really fun, but life got busy and ubiquiti fills the niche between just works, and letting me get really picky with settings.
Fully agree. Sometimes the best equipment is that which is in-hand and thus free.
you can just send vlan tagged traffic across a dumb switch no problem
A small word of caution: some cheap unmanaged switches rigidly enforce 1500 Byte payload sizes, and if the switch has no clue that 802.1q VLAN tags even exist, will consider the extra 4 bytes as part of the payload. So your workable MTU for tagged traffic could now be 1496 Bytes.
Most traffic will likely traverse that switch just fine, but max-sized 1500 Byte payload frames with a VLAN tag may be dropped or cause checksum errors. Large file transfers tend to use the full MTU, so be aware of this if you see strange issues specific to tagged traffic.