So I've not really ever gotten into training/battling too much. I like to have a strong pet for plots and whatnot though. Here's what I have so far

Trident of the Banished One, Phoenix Quill, Icy Freezing Rod of Doom, Amethyst Mace, Armored Groblen, Fierce Ice Blade, Hellfire, Shinwas Sealed Scroll of Dark Magic

Now, most of my armory consists of random thing that I've thrown in there that have a relatively high attack icon (like 15-20ish or more). The trident I got from the bobblehead collection a long time ago and is my main weapon. The quill, I read through a bunch of posts and purchased it to replace my Shinwas Healing Potion....same with the icy freezing wand. The mace I think I got from token shop or something and everything else just had a kind of high icon rate. My pet currently has 19 alchemy points and I really don't know a whole lot about scrolls

Sooooo any advice is appreciated :) Battling isn't something I plan to get too serious about, but there are challengers I'd like to beat for their prizes, achievements, etc. :)

Oh, and I do have an Aemis but can't use it until I'm tier 5

i recommend to pair with your trident. can be bought in battle shop. i use it all the time with my Replica Minotaur Knocker. hardly need another attacker.

is cheap. it gives blessing that block some icons and heal for a few turns.

if you are having trouble with Mechalag, is perfect to fight him.

is a better freezer than Icy Freezing Rod of Doom. but i personally use Icy Freezing Rod of Doom until i can afford Gorgun in battle shop.

is ok and cheap but i personally don't use it much. i prefer Cursed Demon Sword but Cursed Demon Sword will damage 4% of your hp each use.

is ok too if you like. it is just slightly better Armored Groblen, Cursed Irion Chestplate or Shinwas Helmet of Protection, so maybe don't buy it unless you are sure. i can lend you if you want to try. but i think Crystal Ball of Fate + trident should be enough.

my strategy mostly use a lot of healing items since most tier 4 challenger doesn't have high hp. so i use a Gorgun, Shrine of Apollonia, Ruffie Healy Bones, Phoenix Quill, Sparkling Quill and UltimaPlus Tag together with 2 multiheal items.

is a full blocker. very expensive but great item to have even for further tier.

if you don't want spend much, save you sp for tier 5. tier 5 have more worthy and exciting weapons.

as for scrolls, have a look at divine denizhen and death delusion. death delusion has a small chance to freeze. i use both of them all the time even at tier 7. i'm cheap anyway to buy fancy scrolls.

also, equip your pets with bunch of dark potions and pylonics. particularly is useful for you since it boost 100 str and def for the battle.

i am not an expert but these are mostly what i used and it works for me.