Hi, check with nail harmoney what ratio they recommend, I use CND and follow the rule of 50/50 like you said and it has always worked fine for me, though recently with the introduction of additives they say to make sure that the additive is no more than a third, so I wonder if its the same for glitter. Having said that though I have never had a problem mixing my glitter and powder 50/50. Bear in mind that you dont really build structure with the glitter acrylic, you do a very thin layer, then build the nail with clear acrylic over that.
Doing a ring finger in full glitter is really easy and you shouldnt have any problems, I recommend you do your prep and tip, then a very thin layer of clear acrylic on the whole nail, then a very thin layer of your glitter acrylic, then use a clear acrylic to seal the glitter in and build the structure of the nail. Make sure your clear coat on top of the glitter completely seals the glitter in or when you come to filing you will file the sparkle off the glitter and your nails look like you have tiny bits of metal stuck in them.
Regarding your irridescent glitter, personally I'd mix it in with a clear acrylic but thats just personal preference, try both and see which you prefer but I dont think and irridescent glitter will show up very well in a white acrylic.
Alternatively there's a much easier way to do this - do a full set of natural enhancements, then apply shellac and do a rockstar by scrubbing glitter into the inhibition layer of the second colour coat, followed by topcoat (for the full nail glitter) or for a glitter tip do shellac, topcoat, remove inhibition layer, then use shellac to paint french tip on, cure and scrub glitter into inhibition layer then tidy up to create a glitter french. I'd do it that way personally because its easier, quicker, and sparklier.