Kiwi is right about the Ra-tech bolts, right pieces of sh*t they are.
As Tariq says, buy stock definitely, WE's quality control isn't very good so it may last ages, it may last a couple thousand rounds, then upgrade. For the trigger set, go for CWI over ra-tech or just replace with standard WE parts and hope you get a good one. No need to upgrade the bolt though, keep the stock one- not bad and lighter than upgrade ones.