If you buy a package bow, normally the priority of upgrades goes like this...
1. rest
2. sight
3. stab
4. quiver
String update is dependent on the bow as some factory string are good and some are not so good. G5 and prime have excellent string where Mathews and Mission, not so much
A bow never comes with a release (unless it is a used package), you can get a good release right off the get go.
For a great budget sight look here.....
https://www.cabelas.ca/product/11958...me-5-pin-sight