Start with me and I come last,
Add one and I become excited,
Add another and I call someone,
Keep going and you will get something trendy,
Add another and you will want me,
Well now, add another and I will look like a weird balance,
Add another and I'll bring you up,
Yes, yes keep going and, and, and...?
Well okay add another, and there will always be more.
Add the last and final, and I will always go ahead of what you started with.
I will add a hint soon that will shift your thinking in the right direction...
Adding the no-computers tag would make this even trickier.