Honestly, the easiest thing to do would be to use your wife's income, as she already meets the requirements and will have been with the same employer throughout the 6-month period.
I imagine it could be tricky for you to get a new job with only a short time left on your visa, as UK companies may be concerned about whether the next visa will be granted or not... so I would actually consider this option as a last resort instead.
Also, if you are able to get a job that meets the salary requirements, you will need to provide more paperwork and will have more requirements to meet than if you just used your wife's income.
For example:
Using your wife's income
She will need to meet 1 requirement:
1) she has been with the same employer, earning £18,600 or more, for at least 6 months
She will need to provide:
- 6 months of payslips
- 6 months of bank statements
- employer letter
- job contract
- latest P60
Using your income
You will need to meet 2 requirements:
1) you have been with your new employer, earning £18,600 or more, for less than 6 months
AND
2) you have earned at least £18,600 in total in the last 12 months, from any and all jobs you have held in that time
You will need to provide:
- 12 months of payslips, from the old and new jobs
- 12 months of bank statements
- employer letter from new employer
- if your previous payslips were issued electronically, you need a payslip verification letter from the old employer as well
- new job contract
- latest P60 (issued by previous employer and also verified in a letter if issued electronically)
Alternatively, if you have enough cash savings between you, that might be an option too... as the savings requirement for ILR is only £34,600 (compared to £62,500 for the previous visas).