If you really want to save weight, see if you can work in a 1x system. That'll remove a shifter, a derailleur and one or two chainrings. It sounds like you're approaching this problem from the backward direction, which will usually result in lower performance and more cost. That's not the smart way to go. Ride your current bike and begin to save your pennies. Skip beer once in a while and throw the money into a jar. You'll be surprised how much you can save in no time.
There are many videos of how entire full squish carbon MTBs can be built from AliExpress frames and parts carefully specified and purchased over time. All for well under $2000. Start saving.