Is it the gear.... cuz I tried putting on all proto gear and I got put in tier 3 LD.
what determines what tier of LD you get put in.
First, make sure your armor, shield, helm, weapons, and trinkets are specific to the desired tier. I am not sure about costumes, but I am pretty sure they don't affect the tier.
Second, make sure your loadouts are set properly. For example, if you want to do T1 LD, and you have a T3 loadout, just set that loadout as PvE rather than PvP. This way, it won't force you to do t3 lockdown. The highest Tier PvP loadout you have set specifically for PvP determines your tier; if you have even 1 T3 loadout set to pvp, you will be put into T3 lockdown regardless of any other reason.
Lockdown looks at all your PvP(Purple Crossed Sword Icon)-Marked loadouts, even ones that you're not equipped with it.
Just look through all your loadouts and mark any that has 2* or higher gear as PvE.(The loadout icon should become green with the two swords side by side.)
http://wiki.spiralknights.com/Loadout < This shows you what the icons for PvP and PvE should look like.
EDIT: Ninja'ed.
Its gear + loadouts
If you have a different Tier Loadout that is marked as "PVP", you will get put into that tier.