Good job on the new purchase! you've made a wise decision!!
Setting up dongles can be a pain, trust me, i've done it on several machines.
Firstly, most Networks i've come across tend to leave us Mac users high and dry when it comes to support (the price you pay for cheap support staff) The best thing i've found is this: the only thing you need is the driver - don't bother with the 3rd party app to start it all running - Apple's own System Preferences for networks is pretty good at dealing with most things so as long as you can download the driver you should be fine.
You mention that '..the Mac refuses to recognise it.' is that when you're trying to install? if so, that's usually quite normal
Does it see it as an external drive? (shows a disc, as if you'd put a CD/DVD in the drive) if so, try this:
1. Plug in the dongle, access it and run the software install
2. Unplug dongle and restart Mac
3. totally ignore the 3rd party software that was installed
4. Plug in dongle
5. open System Preferences > Network
6. Add Interface: ? not 100% what it'll be called but it should be HUAWEI... or similar - if there is 3 pick the one ending 'Modem'
7. Set the telephone number to: *99#
8. Click 'Advanced'
9. Set Vendor: Generic, Model: GPRS (GSM/3G)
9. Confirm changes the hit dial - and with a bit of luck you'll connect
If this doesn't work let me know and i'll give you some more options 🙂 trust me though... It WILL work eventually and you'll be more than happy to have made the change!!