Are you in the UK/Europe? I assume you are since you mention 220V.
I don't think the small oxys you see on eBay are up to the job.
The Devilbiss ones, of the type that Tuffnells sell (reconditioned medical units)
https://tuffnellglass.com/contents/e...centrator.html are fine for a standard Nortel Minor (I started that way), and would be enough to get you started on a Mega Minor, in soft glass.
You might want a second one to link to it, or to replace it with a 10lpm one, as you get used to the torch and want to do more with it. And if you are starting with boro you might consider 10lpm right away.