Some newbie ship advice:
Modules have a number-letter system, the number is the 'size' and the letter is the rating, with A being the most expensive and highest performing (but not necessarily the best!).
For internal modules (stuff like shields, life support, FSD etc, but NOT weapons) the rating system of E-A usually follows this pattern:
E) Cheapest, worst performance, 'standard' weight
D) Either the same performance as E or slightly better, but reduced weight.
C) 'Average' performance, standard weight
B) High performance, increased weight (but also increased module integrity, meaning they take damage slower)
A) Best performance, standard weight
For trading & mission running (which you said in your OP you do) you want 2 things, cargo space and jump range. To get the latter the general rule is to use D rated modules for everything except the FSD which you want to get to A. A lighter ship jumps further. Weight also includes cargo and fuel, there is sometimes a reason NOT to refuel to max but instead run partially fuelled, if that means a more efficient jump route from the slightly reduced weight.
Special Tip: Cargo bays installed in ships at purchase time are actually 1 size smaller than the module slot they are fitted in (The sidewinder is possibly the only exception to this). For example the Hauler comes with 2 size 2 (4 tonnes) cargo racks, installed into size 3 compartments, which can take 8 tonne racks.
As was previously mentioned in the thread, if you are selling a ship then you should sell the modules inside it first. The reason for this is that modules sell at 100% value, however ships sell at 95% value, but that value includes the modules - so let's say you have a 10k ship and 40k of modules, if you sell the modules you get your 40k back and then 9.5k for the ship, for a total of 49.5k. If you sell the ship with the modules you get 47.5k (95% of 50k).
Lastly, here are a couple of links to sites where you can 'build' a ship.
http://www.edshipyard.com/http://coriolis.io/You should upgrade your starting sidewinder with the cash you have made to get it to here:
http://coriolis.io/outfit/sidewinder/02 ... =.Aw19A===Then use that ship to save up until you can buy a hauler and outfit it like this:
http://coriolis.io/outfit/hauler/02D2D2 ... =.Aw19A===And then use that hauler to make more money, upgrading the FSD until it's A grade, while leaving everything else at D.
http://coriolis.io/outfit/hauler/02D2D2 ... =.Aw19A===Then use that Hauler to make enough money to buy either a Cobra (good all-purpose ship, can be used as either an upgraded trading/mission ship from the Hauler, OR it can be used as a decent combat ship if you want to try out some pewpew), or a Viper (more specialised combat ship than the Cobra, but can't haul cargo for toffee)
Final Tip: ALWAYS keep enough cash to pay for insurance. It might be tempting to fill your cargo hold with a few more tonnes, but you must resist! Never fly a ship after the sidewinder without keeping enough cash to pay the insurance.
