To reach a tech very fast like Stealth, just gather
from early trades to chain RAs around turn 80-90. Prioritize luxuries/ressources selling in the first place then keep
. That gives you 3 chains that propulse you through the tech tree. Don't ally CS until turn 150 or so unless you are very lucky with barb quests. You will reach Stealth under 170 turns because 3 chains can gives you between 15 and 21 techs. Add some GS, Oxford and possibly Sci. Rev. to finish the job.
Bulbing 1 to 3 scientists for electricity is a good thing(you will probably be in the middle of your 2nd chain).