Donation is a Duty. Please decide to donate as per your will/capacity
If you are not a full time devotee and working for livelihood then you must spend a part of your earning for temple activities, or, help them who are already serving and preaching about Krishna. By doing so, you can purify your earning. Make your working spot as the serving spot of Krishna. Make your friends in work spot as the devotees of Krishna. Distribute Srila Prabhupada’s books to them and make them to do the same. Thus, you have made your JOB as the Service for Krishna.
You need not to deal with the big audience. Atleast make your kiths and kins as the devotees of Krishna. Just speak to your friends and neighbours about Krishna and request them to chant Lord’s Names.
If even this is impossible, atleast you shape yourself as a sincere devotee that will attract others and make them think of Lord.
In addition to that, you can make some contribution to the temple every month that will help the devotees there to preach.
This way, you can make your MATERIAL EARNINGS as SPIRITUAL. try to serve Lord in your own set up. So, you do not need to go to forests to perform austerities and devotional service. So, what is the problem in doing our duties and service to Lord simultaneously?
This is what Srila Prabhupada and other acharyas advised. He advised us to make our home and work spot as temple.This is essence of Bhagavad Gita.