How would I prove that I make more money in order for me to sponsor my wife for a green card?

Hello. You can show a letter verifying your job and salary. This should match with any recent paychecks to estimate your annual income. You may also provide assets, accounts or a joint financial sponsory.

You can do that right away, with a letter of employment verification from your employer and a copy of a paycheck stub. IF you want to petition for your wife right away but do not have sufficient income you can also try to get a joint sponsor whose income is sufficient to sign the affidavit of support on your wife's behalf.  That person has to be a US citizen or US permanent resident but does not have to be related to you or your wife.