Welcome to the most fun army ever to come out of the workshop. You won't always win with an ork army, but you'll never lose because orks don't lose! (see page 58 of your codex)
And besides, these guys are just plain fun.
As for you the lists you have been running with, they've got some great potential. I'm not sure what you have available to you for models, but I think wyddr afforded you the use of proxies in your first couple games, so this might be a good opportunity to try out some different units.
Some of the big things we have to look at is the point levels you are playing at.
3. target priority
Orks are not known for their consistent behaviour and its their randomness that makes them such a fun army. At low point levels though, you are relying on every unit doing its job without a glitch. Look to units that help mitigate randomness with re-rolls and just massive amounts of dice.
For example: lootas are great, but can have a lower amount of hits due to their random shot count and worse balistic skill than a unit of killa kans with grotzookas for similar points. You may lose a single point of strength and AP in their firepower, but that is more than made up in their durability.
You did work out some good target priority balancing of your list, as wyddr had to choose between the lootas, lobbas, and orks, but a combination of deploying too far apart and have slower moving units or units that suffered from moving and shooting, he was able to pick apart your army.
The way your current list is setup you would definitely take advantage of using the castle technique. Have your lobbas and lootas in the rear flanks in some cover with the two units of shoota boyz in the center, being able to intercept or counterattack an enemy charging your ranks. There is plenty of firepower to make any opponent approaching pay dearly and you want to get as many turns of shooting in before you have to engage the enemy because you essentially have a gun-line army build. If you want to continue with this type of build there are some great units you could add for the next 250 point jump.
I know it seems like you're trying to assault the enemy with it but hear me out. Put the lootas inside and they have an armoured fire base to shoot from. You have a plethora of weaponry you can add to the battlewagon to turn it into a devastating long-range shooter on its own and with that great front armour, it's going to withstand a lot of punishment. It would make a great unit to anchor your castle with.
2. Killa Kans
Great, cheap armour with better ballistic skill than an ork and is able to move and shoot. Comes with a handy pint sized klaw, that while not as strong as a power klaw, is not unweildy. I almost always take them with grotzookas for the higher strength and templates for greater number of hits.
3. More orks
The best unit to add to an ork army is more orks. The best upgrade for any unit is more orks. They are cheap and plentiful. Face it, you're running a horde style army. The more bodies in your list the better. The best look on your opponents face is always when he says at the start of the game "I don't have enough to kill all that".
Gretchin or Grots, as I call them, are great meat shields, can bog down an enemy unit for a crucial turn or two and can actual do some damage with enough shots from their blastas.
You could go the other way and make a more aggressive assault/drive-by shooting army, but you may need to drop/change some of the elements of your list.
You could put the lootas in a battlewagon, the boyz in trukks and then add koptas, buggies, and/or bikers to fill out the list. The mek gunz just don't seem to fit in that list, but at a higher point level, say 1500+ points, they'd be fine to put back in. At higher point levels you can have different factions of the army performing differently. Half the army could castle, the other could be on the offensive. There are many techinques, hammer and anvil being one of them, that would work with that style of army, but I think at this low point level you need to choose either a stationary/attack from afar list or a mobile/bring the fight to the enemy list.
Let me know if any of this piques your interest and I can go into more detail.
Welcome again to the ranks. I look forward to seeing your next showdown.