at your stage what you want to do is build lots of Small Cargos and Light Fighters so you can go after small targets and just try gget as much extra income as possible. to raid though, you need to do a few things first.

upgrade your computer tech, for every level you get it increases the amount of fleets you can send out by one. if you can get it to level 4 you'll be able to send out 5 fleets at small targets, making up to 20k each round of attacks. This will almost double your income, allowing you to get more and more. Pretty soon you'll be getting more income from raids than mines.

If havn't gotten espionage probes yet, get them. you need to be able to see your targets. send out 2 at a time, and keep increasing your Espinage level so you can see the targets fleet and Defense.

as for your fleet composition. early on its ok to build a few SCs and go after very weak targets without any D or Fleet. after a while these easy targets become harder to find, so build LFs. A good ratio this early on is about 3 - 5 for every SC. Eventually though, as the defenses you go up against become stronger, you'll need a greater ratio of LFs to SCs, and also need to start investing in bigger ships like Heavey Fighters and Cruisers.

Also Download Speedsim. You'll need it to simulate whther your fleeet will survive any targets D. the link is in the resources sticky.

Once you get a steady income you'll be able to start researching colony ships, which are the next target. Colonies mean more mines, more bases to attack from, which means more income.

you can't know anything more about a player outside the top1500 other than that he is unranked. that's why blind raiding is risky. you need to go after probes asap, then just probe the hell out of anyone unranked an you'll find suitable targets.