I'm looking to buy a small condenser mic for around $ 150 and was recommended by Sweetwater the Avantone ck1. ...anyone have any experience with this mic or have any other suggestions? I'll be using it mainly for acoustic guitar , but also fiddle and banjo ...maybe drum overheads...

I do not know that mic.  I use a Rode NT-2A and an Electro Voice RE20 for almost everything (except live drums which I don't use often).  Both are about double your price point.
 
Sweetwater's advice is usually good, though, so I doubt you will be disappointed.  The reviews are really good on tis one:  https://www.gearslutz.com/board/reviews/673952-avantone-ck-1-a.html
 
I bought some mics in the $100-150 range without advice before and found them very harsh and spitty.  In the future I will seek recommendations and read the reviews.

Audio Technica AT2020 is suiting me fine and its in your price range.

For being mics in this range I recommend watching Musician's Friend's deal of the day...
http://www.musiciansfriend.com/stupid
 
They offer some pretty good discounts on mics you might want from time to time.

Ditto that , I got these excellent CAD mikes for like under $40. I use them a lot. They are always putting them on stupid deal. I also ditto the AT2020. 

Hate to admit it.  HATE!. And I am a serious gear snob, so I would probably not buy one myself, but the Behringer B-5 sounds every bit as good to me as a Neumann KM184 on acoustic guitar.  For $69 each.  That is a disgusting deal.  
 
You didn't hear that from me.  
 
Nothing beats Schoeps CMC54 and Sennheiser MKH8040, though.  You did hear that from me.  

rumleymusic
Hate to admit it.  HATE!. And I am a serious gear snob, so I would probably not buy one myself, but the Behringer B-5 sounds every bit as good to me as a Neumann KM184 on acoustic guitar.  For $69 each.  That is a disgusting deal.  
 
You didn't hear that from me.  
 
Nothing beats Schoeps CMC54 and Sennheiser MKH8040, though.  You did hear that from me.  

LOL

I'd recommend the CAD e70, which comes with both a cardioid and omni capsule. Fine SDC. And it only costs like $70 or something in the US. 
 
Some say they're too bright (on the internet, stuff is generally too bright), but it is in fact way mellower than say, an AKG c451. I realise that this is like saying it's way less deadly than a hydrogen bomb, but what with the AKG being a studio standard and all...
 
I much prefer them to my Oktava MK-012s on stringed instruments. Not as drum overheads though.

I like the SE X1 and it sounds great on all different sources. Not as harsh as the CK1.

dappa1
Audio Technica AT2020 is suiting me fine and its in your price range.

Me, too. Never a problem with it and it's pretty clean. Some reviews I read before buying it said it's very close to having an AT4040, but at a lower price.