A good bit of advice for showcasing your portfolio of work is to only have your best, most current pieces in it. If you find yourself making excuses for your old art, "Yeah I know the coloring isn't great, but it's old and I don't color like that anymore," then you should really just take it out. It is infinitely better to have 4-5 strong current pieces that showcase your current skills than it is to have 20+ pieces, most of which don't reflect your current abilities.