There's no need to pay for such things. Just study exiting Gundam designs and find what make you click into them, then attempt to implement those details in your own designs while trying to make them fit together.
For what it's worth, I think mecha designer usually work in thumbnails first. Basically, they draw quick silhouettes of the design they envision and then work they way through the detailing with several iterations, each time adding/modifying details. Look for videos on this subject and you'll see it is far easier to do than it may sound at first.
As for the design you posted, well, it looks more like a preliminary sketch than a design truely speaking. I mean by this that it lacks the appropriate amount of details to make it really shine. Though, it is an interesting start as it is very thin which is quite uncommon. Check out the Nobell Gundam from Mobile Fighter G Gundam for an example of a light Gundam design. If memory serves, the Seravee Gundam from Gundam 00 has a specific configuration where it is also very thin.
Coming back to your work, there is an obvious discrepancy between the overall roundness of the head and the squarinesh of the body. They are interesting taken separately but once put together they don't really fit, the roundness of the head clashing with the squarinesh of the body. As the latter looks quite classic, I'd recommend you try to develop a somewhat organic/biodesign Gundam. For example, you could check out the Victory Gundam mech designs as references...
The legs look way oversized too, making the mech' looking like some sort of Pokemon-like mecha. Nothing wrong here in itself, but it doesn't really fit the Gundam theme. Of course, mechas often have oversized legs as it makes them look powerful, but not that much. Note that a quick and easy way to make the legs big without drawing them big is to shorten the forelegs: in the human body, both have approximately the same length so shortening one will make the other looks bigger by contrats, and same thing with the arms by the way...
Actually, a mistake to avoid is to try to mimick the normal proportions of the human body. Mechas often are disproportionate in fact. For example, the torso usually is short and broad with the shoulders very big and the waist even thinner to make said torso part even stronger. In the same way, the head is significantly smaller to make the torso and shoulders more stronger-looking, like in super heroes character designs actually.
One last thing, don't forget that Gundam usually have a double-fin antenna on their head. Even the Uncorn Gundam, when going into full combat mode, sees its one-fin antenna separating into two. That's an emblematic part of a Gundam design that a designer should always respect.
Here is what I can tell you so far. Oh, and don't bang your head against the walls, good mecha design IS hard to do, most renowned mecha designers having spent entire years of their life to develop their skills in this field...
