You have many options for mb:
Starting from c4,c5, Xentry VCI and many more
Even Chinese clone works fine
You can search on Amazon, ebay, AliExpress….if you need oem you also register with benz and get an oem kit but its an hassle job and expensive too.
Look here for experience mb star interface
1. SD connect C4 with XDOS
SDConnect (C4) with XDOS/Vediamo/DTS Monaco would be way below your budget and the HW should handle most of your tasks. However some SW updates for latest MB models would ask for DoIP support and DoIP is missing from all (decent) quality SDConnect clones.
A genuine eCom could be an option but it does not cover all older cars.
2. Original used SD connect C4 with DOIP
You can buy original used SDCOnnect units with DoIP inside or new Xentry VCI but you need find original unit. Here are units which looks like original but it′s not. It′s not the same update software for Bmw and for MB because MB official way is online coding and programming they have not offline option for software update calculation in their diagnostic software. Can be used software like Vediamo or DTS Monaco for programming but you need to know which software is update for control unit. Officially is everything calculated in online MB world.
But if you have budget limit, you can try Chinese clone SDConnect C4 doIP from a Chinese dealer like https://www.obd2tool.com/goods-10229-MB-SD-Connect-C4-MB-Star-Diagnostic-Tool.html
The product description in the store (first photo) shows the full chip PCB.
3. VCI C6:
The C6 device unlike any other devices:
The device “C6” have a particularly rules first of all the reseller must send you the driver’s files for each version because it is not like C3 , C4 , C5 devices working with any version
like, if you have xentry version 12 2018, and you want install “Xentry” versions 05 2019 or 09 2019
you will have to have the driver files for versions 05 2019 , or 09 2019 from the manufacturer
4. Vxdiag Benz C6
I have the older VCXDiag C6 (the one without USB and ethernet on the side) and other than DOIP it has worked well for me with my May 2015 MY2016 W212 and I last used it about 8 weeks ago. I only use it personally on the one vehicle and not commercially though.
I don’t use the WiFi side, only ever the USB or ethernet cable – I tend to stick to the ethernet cable.
I never could get DOIP working – it passed the tests once in Xentry from 2018 with the manufacturer supplied HDD but as soon as the drivers updated it never worked again with that version and I spent hours messing around with it. I think they have an additional fudge in place somewhere to make the DOIP tests pass.
The supplier did say that the new disk they had would work with DOIP but I never sent this one back to test it – I should get around to it at some point. For now I just used a fresh Windows 10 64 bit install with Xentry 07.2019 and the VCXDiag drivers and Xentry worked.
I got the MB dealer to update my NTG5.1 in the end.
I need to use it later as I’m having some hesitations when pulling away, not sure if it’s a fault or just need to reset the transmission.