I wany to participate because I want to encourage others to grow in Christ. I am much less concerned with the pastor's doctrines, barring something extreme.
Talk to the minister of the church you currently attend about opportunities to serve.
I suspect from how you've written your post, that you do not regularly attend church.
OK let's turn it around. Image you are the minister of a church that you've worked hard to build up, when along comes someone with no history of regular attendance at a church and says they have a gift they want to use.
How would you respond?
Most ministers will ask you to demonstrate your commitment to their church, by regular attendance, volunteering for those jobs people don't like doing and by how you contribute to prayer meetings and bible studies.
If you are not looking for a recognised position, which my comment above is about, then being an encouragement to a congregation means getting to know them and them getting to know you.