First of all, I'd like to mention that at low levels the resists don't really matter - so until lvls 75-90 just pick whichever one has more useful offensive capabilities.
Since this is the main criteria, I'll start from here.
Torontosaurus Rex or Headless Horseman (Frost's storage). Both have strong weapon-based fire skills.
Moglord Tortress (Frost) has the strongest water skill in the game.
Grenwog Rider or Tyrannockicken Rex Rider can be used for a strong wind skill. Cyclone Wyvern Rider has a poison skill, though the armor caps at lvl 133.
The only freely available rider armor with good ice resists is Warg Rider, but it doesn't have a skill or anything outstanding. Graverider can toggle to elelock to ice, but is premium. There's also the seasonal Reigndragon Rider with a Burn skill, but it's FD.
Earth has a number of rider armors, but the two worth checking out are Grenwog Rider (mentioned above) and Chimeran Rider with poison and fire damage skills.
Champion Paladin Rider is an FO energy armor with a spell-based skill. At later levels you can also pick up Volt Rider for elelock and paralysis.
Either Champion or Crimson Paladin Riders would work for light.
Nocturnal Knight Rider is a fairly generic FO darkness armor with increased accuracy. Alternatively, you can pick up Nightmare Wyvern Rider for its poison skill, but it both costs tokens and caps at lvl 130 (power level 140).
I'm going to presume you want something other than a generic inventory full of bloodblades. ;) For thematic purposes, I'll focus on ones that have Rider triggers.
Zealous Paladin Lance does 7.5% more damage when using Rider armors.
Serene Paladin Lance and King's Lance gain damage and bth respectively when used in Rider armors.
CycLance gains bth in Rider armors.
I can't find any ice weapons with rider triggers, so just use Shattershard Glaive (a bloodspear from Frostgale Intro) or Lance of Frostval Past for qc EleVuln. You can also pickup Canrnifex Spear if you want some compression.
Gloom Glaive gives you harm compression.
If you switch you Thundersplitter into its ranged version, you'll have both an autohit weapon and a burn-inflicting spear.
Radiant Paladin Lance has a trigger to deal bonus damage in Rider armors.
Darkness doesn't have any rider triggers, so pick up Agony's Embrace or Dark Glaive of Victory. Alternatively, you can set this as your no-drop element.
Since you'll be using ranged weapons, you'll need to have high dexterity, which allows you to take advantage of shields with on-block effects.
Shield of Agony's Blood. Gives monster negative bth lean and damages them a bit on block.
Figurehead makes the monster unlucky when you block. Alternatively, your Hyperalphean Skjoldr can come in handy against nukes.
Fujin gives you a Dex drive for bonus blocking, bth and Ranged damage.
Cryo Chrono has a chance to paralyze the monster on block. Horo Show shield (damage and heal sp on block) or Defender of Frostval Past (qc MRM boost) are alsosolid options.
Chieftain's Ironthorn has a Str drive for extra damage.
Pixel Guard has a chance to Blind the monster.
Moonfang Omen heals sp when you block.
Bloodfang Omen has some lifesteal when you block a hit.
Since you don't plan on any Cha, Thernda should be the only guest you need.
Skill Scrolls, Warmaster's Burst and Runic Binding give you nukes for whatever element you feel needs one.
Your Soul Burns Bright as a Beacon gives you an hp-costing light spell once you start putting stats in End.
Your Body Heals at the Speed of Light uses Dex for stats and multiplies healing by monster's LightRes.
The rest of your slots go toward support spells. Here are some options:
- Moonwalker's Grace and Buffalot Beach Bod (premium) give you qc Dex and Str boosts respectively.
- Edoc Imanok gives qc MRM boost.
- Absolute Darkness boosts short term damage and long-term blocking.
Nothing really beats the Thernda pet (premium).
Essence Orb, of course.
Since all your your weapons would be ranged, Blood Contract, if you have it, or the Scope misc if you don't, should cover your damage boosters.
Goggernaut Helm gives +10 bth, which tends to be very useful at lower levels. Your Helm of Frostval Past presents a nice alternative.
Since Frost is not using your Prime Chaos Orb, transfer it to this character. The shuffling of the resists allows you to make the monster vulnerable to your armor element (and thus armor nukes) as well as increasing all damage you deal to it.
Zfinity gauntlet of power allows for further damage stacking.
Morningstar Helm makes you immune to paralysis.
Sight Beyond Sight, Hairmuffs or your gauntlet of Time allow for further focus on blocking.
Hyperalphean Charm inflicts the monster with Fragile, which can be rather powerful at lower levels.
Hope the info was useful, and don't hesitate to ask if you have any questions!