This is unbelievable.

Jumping without scouting ahead has caused me many a setback, my friend.

Always, ALWAYS, jump a few ships before the  main fleet. 

If you built your economy along with your fleet, it shouldn't have cost you the game, however.

You should have been able to pump out a protection fleet and get a good defense front set up to hold them back until you could fully rebuild....

Seriously, and the most effective way to do that is (in my opinion) make starbases and give them the full trading upgrade.  This saves your logistics slots for more important things like refineries and research stations.  The tactic also requires you to build a starbase that you should build anyway so helps add impetus to building your defenses.  A stardase with two upgrades to trade gives you 4 cps which is what?, 3 trading ports?  

all you need to do to gain the time to do this is set up your first four starbases at the star (unless there are wormholes you didnt mention)  Backfill the planets after youve set up those.

And yes, ive conquered the other players planets then gotten ambushed.  But if your fleet is winning, just keep it at the same size and just pay for replacements.  This gives you excess money to spend on your starbases weapons and shields.  If you have starbases at all your planets (which you should if you want money through trade) this slows them down plenty.  Then once you can actually see what the enemy fleet is you need to build a quick replacement fleet.  Put them a phase jump away from a system with a starbase in it that the enemy will go after (the jump has to come out near to or right behind the enemy fleet).  The moment they arrive, trap them between your fleet and the starbase.  It also works really really well with advent starbases that have meteoroid control.  THEN CRUSH THEM TO A PULP!!.

And when i had this happen to me that's exactly what i did.  their fleet outnumbered mine two to one with superior capital ships because i had suffered an absolutely total defeat.   (they trapped me with phase disruptors and gravved me in place.)  It works extremely well, especially if the starbase is upgraded with full weapons and ship production facilities.  Just crank out hundreds of missile frigates.

And im talking a huge fleet.  this game lasted 6 hours (Gateway).  the enemy fleet had 4 desolators 3 evacuators 5 carriers (damn bomber spam) and a destroyer.  It had about 150 light frigates, 150 assailiants, and about 70 of everything else...  It was slowly crushed into dust.  Also, get quite a few marza dreadnaughts to deal with such fleets with their missle swarm and, more importantly, their radiation bomb.  Its VERY effective.

of course you could always rush them instead of all that but wheres the fun in that I ask you?

Oh, and before i forget, a novalith cannon is pretty effective at disrupting them.  There is also another major bonus.  If youre nuking the vasari with it, instead of opening a phase gate anywhere, nine times out of ten they'll jump to the planet with the novalith.  Defend it successfully and youre set.

(by the way dont blame me if this doesnt work cause i rarely play on anything other than hard difficulty.

I just hate it when the other team has economic bonuses.

you also want a planet with 6 frigate factories somewhere to make your replacement fleets.

This is a MUST in case of utter disaster.

Have you played serious games? Trade ports are almost always more profitable than refineries in unmodded Sins, and the Starbase upgrade is much more expensive.

yeah, but you need starbases anyway.  and also, when you have the space and the money, building a few scattered refineries is very useful.  Personally i dont like to spend my time spamming the "buy metal" button.

In smaller maps especially, it is better to make starbases than 3 trade ports which take up way to much logistics.

Yes, I've played many multiplayer games with my friends and random people.  But he seemed to be referring to a fight against the AI, so i gave him effective anti-AI tactics.

And I'm the sort of guy who stays at the knifes edge of destruction to make a massive economy and crush the enemy later.  You just gotta be really careful about scouting the enemy fleets to make sure they don't get too gigantinormous.