Find a bike shop that you feel comfortable with (friendly helpful employees). Tell the owner/manager what your goals are, how often and where you plan on riding and your budget. You should find a decent bike for $500-700. Test ride all the bike they suggest and any that you like. Buy the one you feel comfortable on.
If you don't like the shop or the employees, keep looking for a good shop.
Good luck and have fun.
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.