I'll compile some ideas for expansion here if you like.
The GVPs are usually nice expansions, with some caveats.
For a starter, it's a great thing to have a HDD solution available.
Regarding the GVP SCSI controller, you could check how much RAM is installed and max this out to 8MB.
This would save you the use of the second RAM card. The bonus is that the GVP can access its own RAM a bit faster.
Please check: is the SCSI terminator soldered on?
Or does it even have an internal HDD?
If you want to use the SCSI2SD, you need to make sure you have a cable for internal use and that there is no terminator internally.
TBH, if you can add the SCSI2SD, you can back up anything directly to the SD. No need for the parallel-port-solution. Its waaaaay slower anyways.
If you are into WHDLoad and programming, I'd recommend a Kickstart switcher.
That could give you 1.3 and 3.1.4 via a switch.
For ROMs you may have these options:
Amiga on the lake sells (sold?) 3.1.4 ROMs
Hyperion sells 3.1.4 as a direct download
If you can by yourself or have someone to write an EPROM, you could use this thing here or similar variants from Amibay:
ROM-Switcher for EPROM
And I would highly recommend to get an accelerator with at least an 68010.
This will allow the use of the WHDLoad "Quit"-key. On a plain 68000, you'd have to switch off the machine.
A nice start could be this one
Generally, I would highly recommend getting a 2-MB ChipRAM expansion such as these:
Version 1 Amibay
Version 2 Amibay
Version 3 Amibay
If later on the GVP is not appropriate any more, for mass storage / IDE, you could either get an accelerator with built-in ports or get this new Buddha
In order to attach a newer VGA monitor to your beloved Amiga, I can recommend this nice expansion "Indivision"
You could then later upgrade to a Graphics card ("RTG in Amiga-Land"), passing through the picture of the Indivision, like this one
The additional graphics are added via a driver.
If you want Networking, here is a great option
The XSurf has the great option to be expandable with USB