Right now I'm saving up for two mics to record my acoustic guitars in stereo.
Any recommendations? The cheaper I can get away with the better. Any tricks
I should know about?

 

I use these:

Lauten Audio LA-120 Small Condenser Microphone Pair - Black https://a.co/d/cPPpnMF

They make excellent overheads but I like them on acoustic very much.

 

What about a pair of this ?

 

Also an excellent choice

 

Although I've never used those AKG 420 mics it isn't a bad idea to have multi-pattern microphones. If you bought them you would have the option of experimenting with mid/side (one mic in figure 8 with the capsules perpendicular to either a cardioid or hypercardoid so you can blend to taste for your stereo vibe in the mix) recording which is a nice option to have. An omni pattern is also nice to have if your room is decent.

I myself don't use a same stereo pair and normally use both a large and small condenser using a few different techniques to capture an acoustic guitar performance.

 

Same. I like to use a Lauten and an AT 4033. Or I'll do 1 Lauten in mono and double track. BTW the Lautens have swappable capsules for pattern.