Echoing what weremole said, if you want a comic portfolio you have to be placing actual comics into your piece. If you're looking to do covers, you need to be putting in covers. If you're doing sequential pages, you need to be putting in sequential pages. One or two pages of character design/painting/figure drawing is good and fine and all, but do not load up your portfolio with 20 pages of pin up art if you're trying to apply to do sequential pages. Most portfolios you should aim for 15-20 spreads of your best work and ONLY put in your best work. Your portfolio is judged on your worse piece, not how many pages you can put in it.
Normally for comics, I would put in 3 short stories (3-6 pages give or take) with different types of storytelling. This doesn't mean three fight scenes or three "I'm staring at you for 5 pages and then kiss you during the last panel" stories either, show that you're comfortable telling a story.
And for your lettering/inking portfolio...use your best judgement on that. I would say make two different portfolios geared for lettering and inking, where you can reuse a lot of spreads for each portfolio.
Comics, comics, comics and comics. Anyone interested want to see your storytelling chops since that is what the actual work is about. A combined lettering and inking portfolio with different folders could work.