From reading the post it's obvious that many people have issues with tech research. The most common issues are:
1. I am falling behind in technology.
2. The tech trees are too complicated.
3. How do I decide what to research next?
4. What is the best research path for whatever?
From what I've read in forums and from my own personal experience most veteran 4x gamers do not pay much attention to tech trees. They adjust thier tax settings in a manner that gives them the most income possible while keeping morale a little over 50%. They adjust thier manufacturing ability as close to 100% as possible. Then they chose slider settings to give them adequate military and social production while investing most of thier resources into research. Finally they choose to research techs with the shortest time remaining, this is done because it is better to gain 8 techs in 8 weeks than 1 tech in 8 weeks. Done correctly you will be a little behind the AI at first but you can quickly surpass the AI in influence, economy, and technology. Which means you can easily you can easily create a larger more advanced fleet faster than the AI.
This is an example of the settings I prefer to use (they must be adjusted from time to time as the game progresses).
60% tax rate
55% morale
100% manufacturing
15% military
20% social
65% research
This should make a few techs available with 1 or 2 weeks research. If you stick with this method you will almost always have techs available in 1 - 3 weeks.