|Your 2124 is plugged into the router...........correct?|
If yes, then your new switch should also be plugged into the router and not daisy chained into the 2124. Daisy chaining causes an aggregation of bandwidth. Which is to say, the link from the 2124 will not only be carrying the load of it's own traffic, but also that of your new switch as well should you daisy chain it.
Whenever possible, one does not want to daisy chain switches.
When you say, "We are having a new phone system installed within the next few weeks..." I'm guessing you're talking about a VoIP system. If so, will it require VLAN tagging? If yes, then you'll need a managed switch. So make sure you understand fully what your new phone system will require. It would totally suck to buy an unmanaged switch and discover you need to be capable of VLAN tagging after spending the money.
Its a growing company so Id definatley need a minimum of 24 ports. if at a later date and i need to I should be able to link another ethernet switch right ? ... like a daisy chain ?
If it's a growing company, do yourself a favor and buy a high-density 48 port switch instead of a 24. This allows for a lot more expansion without having to buy more equipment in a year or two.
As for the whole daisy chainging theory, again, I can't stress enough how important it is to not daisy chain when you can avoid it. If you keep daisy chaining switches eventually you hit a saturation point where the one that actually has the uplink to the rest of your network can't support the bandwidth and all switches in the chain stop communicating.
Do you recommend a ethernet switch ?
That's pretty much the only option available. As far as I know, nobody even manufactures hubs anymore and even if they do....you don't want to use one. Hubs broadcast ALL traffic to ALL ports on the device. Whereas a switch intelligently transfers traffic using a mapping of MAC address to port number so the traffic only goes where it's supposed to....not to everybody plugged inot the device. With a hub you have all kinds of issues from too many collisions to broadcast storms.