Show Sent Messages in Mail thread (using gmail and imap)

I'm trying to get my email set up so that I can use gmail imap and also have it show my sent emails within each thread. I can see it within "all mail" but not within my "inbox." Also, ever since I started screwing around with the settings my inbox now takes forever to upload mail or to register that I have read it on my laptop and when I send something from my iphone it shows up on my browser's gmail as "sent mail" which it never used to do. I'm just frustrated and would love for someone to tell me their settings if they're getting the thread view to work well and for a quick refresh! Thanks so much!!!!