tech strategies

On challenging, I would say Planetary Improvements, then engines up to Impulse. After that depends on what style of play you prefer. There are a lot of options.

For early military rushes go for weapons and Planetary Invasion. For diplomacy, focus on getting to Spin Control (that's not the name of the tech, but the building). For a mid-game, late-game attack, get Xeno Ethics and Neutrality centers to pull ahead in tech.

Get up to Research Acadamy, then Xeno Ethics, then NLC earlier than mid-game if you really want to pull ahead.
If you get them during the colonizing and early military buildup phases you should be able to pull ahead on everything else pretty quickly.

If you rush buy a few Xeno Labs and upgrade them promptly it should not take that long.

Thanks. This really works.