Im not too sure about how berserk is supposed to be used. For example if I attack with a {glistener elf} and my opponent decides not to block can I in response activate {groundswell} and {berserk} for the win?
How do you active a sorcery? If you mean cast it, you can't cast it mid-combat.
It links to {worldfire} but dont think its the spell you're refering to, yes?
Yeah it's groundswell idk what I was thinking
Assuming you put a land into play prior on the same turn then yes you could cast ground swell then berserk at instant spee before combat damage is dealt to win. Elf would become a 5/5 with ground swell then berserk would make it a 10/5 with infect. Pretty nasty little combo if you can draw the components early and they don't have instant speed removal or something to block with.
Yep. See also:
{Invigorate}
{Mutagenic Growth}
{Giant Growth}
Yup all that works but I'm not by any means short of ideas there's other cards like {might of old korosa} {wild might} and one of my favorites {vines of vastwood} and many many others but lets not spoil all the fun