There's a lot of suggestions so far that say 'oh wow that all sucks, take something completely different'. That's a bit unfortunate, as you probably want to start with some smaller changes and learn over time, rather than go and buy and paint a whole bunch of new models up front. (For those that don't know Robbie is a fairly young guy and probably doesn't have a huge budget for new models)
From what I know about Space Marines, they are generally 'good' at most things, but don't excel at much.
What that means is that they are fairly good in combat, but to make them really good in combat will cost a lot of points and there will still be plenty of enemy units out there that can beat them up no worries.
They're also pretty good at shooting and have a lot of good weapons, but some weapons are more expensive than they need to be. For example, Landspeeders and Predators are some of the better ways to get big guns into the army, whereas devestators are fairly expensive (points wise) for what they do. Some armies like Tau and Imperial Guard can also get a lot more big guns for less points.
Based on this, I think a good marine list will be balanced - that is, have some good shooty units and some good combat units that work together.
The army you have taken has quite a lot of points tied up in combat units (Marneus and his Honour Guard, the Captain) and not a lot of dedicated shooting units (as basic tactical marines aren't usually a particularly effective shooting unit)
Some simple suggestions that I could make:
* If you really like Marneus, keep him (plus he's painted really nicely!). However, you need to be more aggressive with him. Don't be tempted to stand still in front of the enemy army just to use his orbital bombardment - he should be moving fast towards the enemy to engage them in combat! To help with this, I would suggest deploying him in the Land Raider with his Honour Guard.
* The Honour Guard should probably be made a little bit cheaper if you can (not sure what upgrades they have etc), as they will still be able to beat up most enemy units without all their upgrades
* Because you have Marneus in the list, he fulfills the same role as the captain, which makes the captain a little bit unnecessary. He could be removed.
* 1 Biker is not really enough (and also strictly not a legal option, as a unit of bikes starts at 3 models ). If you have more bike models then include them, otherwise leave this out.
* I would probably also make a choice between the terminators and the dammed legionaries, as they may both fulfill the same role.
With the points that you have saved from those changes, I would suggest:
* Some weapon upgrades on your tactical marines and terminators. A power fist in the tactical squad will really help when they get into combat
* Some more shooty units. This could be things like a Dreadnought with Lascannon and missile launcher, some Landspeeders with weapon upgrades, some predators or whatever.
* Upgrading your landspeeder with some better weapons. A single basic landspeeder with heavy bolter usually won't achieve much by itself. If it has a multimeta though, it can potentially blow up expensive enemy tanks (for example). Upgrading it with a typhoon missile launcher can help it destroy enemy transports like Rhinos and also make it kill more enemy infantry. You can often buy just the extra upgrade bits for a typhoon missile launcher from trademe for just a few dollars and glue them on to your existing model. Same with a multimelta.
Tactics wise, I probably should have done a better job in our game of pointing out things that you could have been doing. Next time

I'm a bit of a novice myself, but here goes:
* The basic tactic is 'shoot your enemy's combat units, and combat his shooty units'. Generally that means you want to have some fast moving units advance towards one part of the enemy army, while your shooting units try to destroy the enemy transports and weaken the units that you are going to assault.
* Don't be indecisive. Decide if you are going to advance, or stay still and shoot. If your tactical squad is deployed at the back of the board shooting things, don't start moving it forward unless you really have nothing to shoot at.
* Take advantage of cover. Whenever possible, deploy your shooting units somewhere where they can get a cover save, and advance your combat troops in a way that hides them from most of the enemy guns
* Deploy your mobile units behind cover, and move them out in your first turn (for example dreadnoughts, landspeeders or predators). There's nothing worse than your enemy having the first turn and using his big weapons to shoot all your tanks out in the open before you've even had a turn.
* Get your fighting / close combat units into combat as soon as possible. The longer you spend moving around the board before you start an assault, the longer the enemy has to shoot you. This is why transports are so important.
* Even though the Landraider has some guns, its main purpose is to get the guys inside into combat quickly without the enemy shooting them. Don't be tempted to move slowly and use its guns until after the unit inside has jumped out and assaulted.
* Even though you have troops that can deepstrike, its not always the best decision. Sometime they're better off being deployed on the board at the start.
Hopefully that helps

As for Orks, I have no idea

p.s We'd really appreciate it if you took the time to write out your units names fully and clearly. We try and avoid 'txt speak' on the forums.