You don't have to spend a lot of money really, but it is recommended to get a standalone grinder rather than a grinder+espresso combo because it means you can upgrade/replace the parts separately. Also most of your budget should go to the grinder, not the espresso machine, since that's the part where money gets quick returns on quality.
I bought a Gaggia Classic Pro machine (~425$), which is perfectly adequate if not the most attractive one, and a Sette 270wi grinder (~450$). They have been completely successful so I have no intention of upgrading.