I believe the tittle itself is sufficient.
I'm currently learning GUI programming using Tkinter in python.
I actually wanted to comment this (but seems like i don't have enough reputation), so here is a simple breakdown.
tkinter is a really nice library (it's beginner friendly - fairly customized), I will highly recommend sticking with tk (because u r already learning it - it will totally comply with your requirement of less resources' consumption ).
I would suggest you to give a try to kivy - if and only if u wish to target mobile devices - it allows native development. Although it uses fair amount of resources which might -in some cases- overlook your system resources.
NOTE: Having said that, if you you require apps with powerful GUI experience, PyQT is definitely a better choice but from what I know, PyQt may not be able to fulfill your priority of less resources' consumption.
Which cross platform GUI toolkit to use if less resource consumption is a priority