Hi. I need help. I've only had Pokemon Sapphire since July. I've already..

Get an evolved Zigzaggun and he'll pick up stuff while you travel

Ethers and elixers are scattered throughout Hoenn and can also be obtained by showing the brothers who like large shroomish/barboach the largest corresponding pokemon they've ever seen. However, you don't need these to win if your pokemon know moves with a respectable composition balance (i.e. pp and accuracy/constant strength versus power).
Your theory is correct in some ways, but also needs some modifications. Your pokemon don't need to be at the highest possible level to defeat any pokemon, just high enough to give them a reasonable margin for error. Also, power-ups don't usually raise anything but happiness by a worth while amount and potions are usually unneccessary if your pokemon know good moves and hold the advantage over your opponent. Instead, a better choice would be to use the majority of your money on TMs to improve your pokemons' moves and then use the remaining money to buy healing items if you believe them neccessary.
Finally, my opinion of your team: your pokemon are mostly fine, but some of their moves are appalling. As an example, look at Chico's moves-not one is great in the pokemon league (one exception: mirror move would be fairly useful against Drake). Just about the only way that you will be able to defeat the Elite Four is to modify the moves your pokemon have to effective combinations. My suggestion for your team is to train Chico to level 59 and let it learn sky uppercut, then delete the rest of its moves and teach it flamethrower, arial ace, and a move of your choice. Then teach Enriqai thunder (which is automatically accurate for kyogres) and surf over sheer cold and hyrdo pump. Then put Chico in the front of your lineup and take on the elite four. If you switch the order of Chico and Enriqai whenever you defeat an Elite Four member and use the best possible move on each opponent, you should do rather well. Finally, keep all your HM moves (excluding surf and, if the pokemon is a flying type, fly) on weaker pokemon so that your fighters remain unhindered by weak moves.

A better way to get all your pp back is to get lots of leppa berries by talking to
1) A man in lilycove city, next to the move deleters house
2)A girl in route 120, next to a set of stairs
3) a girl in sootopolis city; use surf and go past the gym to the opposite side of the pokemon center
4)Berrymasters wife and berrymaster; say anything to the wife and you may get lucky
5)The flower shop; one of the people inside it
6)A girl in route 11 next to the cool trainer
7)a boy near lannete's house

After you get some, plant them, water them at least 3 times and wait till the next morning and they may have sprouted.

hope this helps