I am a beginner too (about 1 year) and here's what I do that works very well to get my chord change speed and accuracy to increase:

Take two chords, say c and d. Put a timer in front of you set for one minute (I use my smart phone). Start the timer and start changing between c and d chords. Count as you go, for example, you strum the c chord, that's 1, you go to the d chord, strum it, that's 2, you go back to the c chord, strum, that's 3, etc.

After one minute, let's say your count is 25. In a notebook make a heading entitled, "C to D Chord Change". Beneath the heading write the date and 25. The next day you do the same C to D chord changes for 1 minute. Let's say you are now up to 26. Write it down in your notebook. I usually will be able to get up to 50 or 60 speed chord change count withing 3 or 4 weeks.

The great thing about this technique is you can see your improvements over time because you kept daily notes. I love to see that 2 or 3 weeks ago I could only do 20 chord changes in 1 minute and now I do 35, for example.

Of course, keep a record for other chord changes (Em - C) (Em - D), (Em - G) (C - D) (C - G) (D - G)