Tip #1: Don't watch the vids on the character forums. Instead, go into training mode and experiment with the hitboxes of Samus's moves. Get your spacing right. This is the time to also learn Samus related techs.
Tip #2: After gaining high level control over Samus, get into friendlies and learn to read shield habits. In turn, also learn to not resort to shield/spot dodge/air dodge/roll. Space better. Know that shield is your tool for reading and punishing, not a shell to hide in.
Tip #3: We do not currently have accurate frame data on Samus. I have valuable information that I don't share on these boards. Hit me up on AIM to learn how to utilize the hitlag/shieldlag on her moves best with Samus.
Tip 1 was for you to gain the tech skill to use Samus. Not much is needed, but I can't tell you how many times I've ****ed up an up+b OoS and it turned into an aerial up+b. Or when I messed up a missile cancel. Or messed up an instant double jump z-air into a grounded grab. Tech skill, little or not, matters. That way, you know your mistake wasn't technical but judgmental.
Tip 2 was for you to advance in today's metagame. You have to learn how to go on the offensive, how to rack damage, and how to use your range to your advantage. Be sure to save your friendlies. You don't need to post them on youtube unless you're seeking criticism, but rather observe why you're getting hit and why you're able to hit them. The vids on the character forums will not help you as much as you going into youtube and watching the latest vids that represent today's metagame.
Tip 3 was for you to know there's help and hope for the character. But for all the advancement in other character's metagames, Samus has had little due to the boards being unable to collect the needed data. There are certain things that have been discovered that aren't utilized yet. You need to learn not only the character, but the game. Sooner or later, you'll need to know frame data on other characters as well, if only the generic stuff.
Finally, pick a character you like. If you really like Samus and are willing to take her far, then you need to put effort into learning her metagame and how she competes with everyone else. A lot of data here is outdated. Go do your research yourself, watch current videos, they don't even have to have Samus in them, and imagine what Samus would do in those scenarios. Picking up a character to main is never easy. The players that place high aren't doing so because of their character solely, but because they put hundreds of hours practicing and learning. You need to be ready to travel and spend money if you want to get better. Hopefully you're in a competitive region. If not, forget competitive gaming.