Since you requested it, here is my no BS answer to your inquiry based upon 35 years of rod building and 48 years of fly fishing.
Cork quality is directly proportional to cost and the best cork is not available as pre-turned grips, it is only available as individual cork rings that you have to turn into a grip either on the blank (my preference) or on a threaded rod or mandrel. However, poor quality cork is not going to effect the preformance of the finished rod, just remember to fill in the rather large pits of the lower quality corks with a cork dust and glue mixture.
In guides, avoid unplated snake guides because they will never hold up. In fact, unplated snake guides will begin to groove within a year or two. As to which coatings, platings, brands, single foot, or double foot are better, that is entirely up to you. If you want to use single foot ceramic or SIC guides instead of snakes or the REC REcoil guides, go right ahead, they just cost more. For strippers, either ceramic or SIC, frame color your choice. For tip tops, again it is entirely your choice, traditional fly loop top, ceramic or SIC, or REC REcoil all work well.
If you are looking to get the most bang for your buck, use cheap pre-formed cork grips, chrome plated snakes, hardaloy stripper, loop tip top, and Fuji or Pac Bay graphite reel seat. This will give you a serviceable, although not the prettiest, good casting rod that will preform very close to one made with SIC strippers and the snake guides with the harder platings on them at a lot lower cost.
Remember two of the easiest places to save money when building a rod yourself are the reel seat (the Fuji and Pac Bay graphite ones are typically around $5.00 or so (instead of the $25.00-$50.00 for the top-of-the-line nickel silver with wood insert ones) and through using hardaloy instead of SIC strippers.
Me, I prefer to use top quaility cork, SIC strippers, snakes and reel seats; but if cosmetics don't matter to you, they are not necessary.