Let me start with what parts do you have laying around? What is your internet connection speeds? Do you have a decent wireless router? In general a dual core processor and 4gb of ram with a dual intel gigabit nic will handle pretty much all your gonna throw at for the most part. If you can find and old dell sff with and i3-2100 and 4gb ram with a 250gb hard drive from office surplus. Buy an intel nic whether that is a dual or single would possibly be your best bet to stay under budget. There all also some very cheap amd surplus mobos with integrated cpu that are on ebay for 40 bucks. I believe there is another pfsense thread on here that has those in there.
Ok well the ac1900 will serve you well for the ap for your network. Are you going to virtualize the pfsense instance on your ubuntu server or just use the hardware form your ubuntu server and run pfsense?
hmmm all those are out of your price range but I believe you can find intel atom d525 boards for cheap on ebay and add a dual nic for another 20 bucks. Do you have the space limitation for a case and are you against used parts?
pfsense is picky with hardware because the dev's pick and choose which hardware to support. What hardware they choose happens to be what their parent company sells for profit.
Use OPNsense, it is a fork of the original pfsense and remains true to what pfsense used to be. It also supports all the hardware that FreeBSD supports, does not pick and choose which drivers to include or not include for monetary reasons. It also has a better interface. OPNsese will also not be forcing AES-NI on you with the next version, so you do not need to specifically go out and buy a processor with that instruction set support. I bring that up because if you do go with an Atom D525 CPU, that will not support the next version of pfsense as it does not have the AES-NI instructions.
Im also considering in setting up a pfsense router. For long update support, I thought of picking a cheap R5 or a R3 with integrated graphics (to avoid costs for a graphics card), but read on the homepage somewhere "integrated graphics not well supported" or something like that.
As I know, OPNsense is a fork of pfsense, does it share the same plugins (repository) or have its own plugins? Would the installation routine be on same difficulty level as pfsense, as I´m a newbie to this and grew up with GUIs?
I have pfsense virtualized on an ubuntu 16.04.2 lts, along with 2 other vm's, i have 2 add in realtek version network cards for a total of 3 physical network adapters, the network cards are both trendnet 12 us dollar specials, using an amd 860k on an fm2+ mobo and an old 5650 radeon gfx card. I got a case off newegg for 14 bucks after rebate, power supply was 15 after rebate, the only thing i had to spend real money on was the 3 tb hd i put in for storage, i already had a 60gb ssd and another 3tb's of storage to run the 3tb's in raid1 for nas. I paid 50 for the 860k and the mobo was 35 after rebate. you can literally build a pretty decent home server with multiple vm's for around 150 us.
I have absolutely no issues with pfsense running and working extremely well virtualized.