It sounds like you need to figure out who you'd like to dedicate your english portfolio to. Has there been someone very special who has helped you along your academic journey?
Once you've figured out who has been very significant in your academic career, you might want to make a list of everything they've done that's been helpful or unique. Has she been extra supportive? Has he taught you lessons that stuck with you?
Select a few of your favorite things about the person and write a couple paragraphs gathering your thoughts. At that point, you can either edit the dedication down to one grammatically correct, well-written paragraph, or try forming into the form of a poem.
If you'd like to go the poem route, you can choose to either make it rhyme or be free verse (a poem that doesn't rhyme or have a set pattern).
I suggest having a friend, parent, or trusted adult (who you're not dedicating the portfolio to) edit it for grammar and word choice. It's always helpful to get a second opinion!
Good luck, and congratulations on finishing the portfolio!