As probably mentioned, it is best to try to train Samus to be defensive and/or campy as possible. Having her being as offensive fighter leave her extremely open to be punished.
Unfortunately, Samus has little to no ability to be able to smash/execute. The best smash moves for her are her Charge Shot (which can break shields at times), forward smash, and her down A. Her other moves, if they don't land, leave her quite open to be punished. Special Note: Might be just me, but sometimes when she forward smashes she tends to aim up leading her to be punished by smaller characters. Her grab even leaves her right open due to the amount of end lag when she misses.
As per to her lack of kill potential, an EPS set is good for her to use to rack up damage - as much as I'm kinda sick of EPS haha... If you want to become more dependent on shield usage, go try to use equipment set (2). I experimented with equipment set (3) giving her more of a "stall heal" set which can be annoying.
Finally, train her to be defensive using the timer method and punish her when she's open. Try to have use her neutral B and side B as much as possible for spacing and harass.