My tactical assignment.
Weapon and Speed are equally important.
Then jump range.
Then scanner range.
The jump range penalty can be delimited with high speed and long jumps have the disadvantage of not being able to do course changes, and not picking of ships in near by systems.
Scanning range in my opinion is the least important tech, as you are fully aware of your own imperial space. You really only need to know what the border planets of your rivals. It can be advantageous to know fleet movements in deeper enemy space, but not nessicary, as its disadvantageous to move into enemy terrority nearer to there industrialized planets.
Economy is the cheapest to develop and the will pay for itself.
Science is the second cheapest investment and can be staggered to every other turn to have a high turn overrate with new tech to make your ships tougher.
Industry is the most expensive to dev., as spreading it through the empire only give you a /mild/ passive defense, but in order to have a decent size fleet you need about five industry points on a planet. Three nearly cuts it, but with five points you have a a decent fleet every two turns instead of 3.8 turns.
Tactical Assignment Continued.
Heavy Industry build in early game seems to be disadvantageous in mid to late game, as you cannot active your reserved fleet with a sense of urgency. Its good for early game, especially if you are planning to invade asap. It however, does leave you with a strong passive defense. Though this seems to be counter productive with the goal of having a high industry rating.
A balance industry and econ, or a heavy econ seems to be more favorable in mid to late game, you can build the industry in a few a few pay periods to match or exceed those of a heavy industry build from early game with the ability to activate said reserve fleets.
The disadvantage is weak mid game fleet, and suitable to early game invasion.
Strong science build from early game, seems to be an uncouth approach, as right now there no means to be a techno broker. It leaves you vulnerable to invasion early and mid game.
Mid to late game, you should survey the galactic map and make note of the unclaimed stars. Most assuredly, these stars have resources less then twenty making them rather unsuitable for infrastructure investment. However, to win the game you need only ninety two stars, and there no need to have the stars be at an infrastructure threshold. Thusly, mid to late game you should make a one ship fleet, whose sole purpose is to claim these unwanted stars.
Systems that are most favorable to invade that is advantageous to the invader are systems with science facilities as they instantly start adding to your research rate, and save you a a decent bit of money.
Systems that are the most detrimental to the invaded, are systems with economy infrastructure. The money gained from such systems, generally cover the reinvestment back into the system, so its of little value to the invader.
Systems with industry infrastructure have an equal loss and gain to both parties, and shouldn't be taken into account if it should be invaded to hurt the invaded or beneficial to the invader. The exception to this rule, is if the system industry is higher then four. The ship replenishment rate is fast enough to partially recover from the loss when taking the system and to add to fleets moving onward into enemy space.
Thusly, I would place three infrastructure in every system with a science facility to give it a passive defense to make it an expensive prospect to invade, without making it to to worthwhile for the invader to risk the investment. If this is taken into account, then science facility become the most expensive infrastructure to construct, and industry being the middle in cost to invest in.
System with no infrastructure and no ships should be given to your one ship fleet to take over in due time. If it has ships then its a jump mid point to further targets, and may be soon vacated. It should be watched for fleet movements.