Its not impossible for a sinx to MVP as I have done it multiple times. I can pawn any mvp with my crit build not as fast as a champ or sniper but the good thing about sinx is that it can kill all mvps as well as steal some from diff. classes. Example: Wanna out mvp a long range char? Wear a pneuma accessory. Wanna out mvp a GS that despe too much or a char that utilizes AOE skills? Use Detale card and hopefully that mvp casts magic to proc ME. Its all about strategy.
You do have crappy gears and as Noireth suggested. Do the f.knight quest, then l.gaunts, l.wep, then get an l.aura, then a legendary lower headgear. You got a wide selection to choose from. I suggest you get the l.balloon. Start voting as well to get a vote king set. Not bad since you got kiel cards hopefully those are not silver, I recommend you sell those and get better cards. Crit sinx wont rely on kiels. You better get some TG or if you wanna PVP as well get some FBH.
Here is a build suggestion
STR = 400 total. Keep it divisible by 10. Ex. STR 262+138 = 400/10 = 40 WHOLE NUMBER
AGI = Until you get 195 aspd w/ or w/o shield
INT = If there is any remaining right after VIT, put some here.
VIT = Do this last with the remaining points
DEX = Keep it as 1. Your a crit sinx not a dag type. You would barely miss unless you are fighting a PD char
LUK = Put some LUK until you get 100 crit. Some are saying 101 or 104 crit is better. Pick your poison.
When setting stats make sure you are on your default gear with the shield on rather than your secondary weapon
Gear suggestion
Upper helm = +10 F.Knight/King* helm w/ 2x Seyren cards. Gives you +8 more STR.
Middle = +20 L.Aura either L.Zod, L.LHZ, L.Myth w/ Gemini card
Lower = L.Balloon w/ Gemini card w/ Gemini card. 2x Gemini card will give you immunity to stone curse as long as you meet the required stat. Dont remember what it was though. If you dont want stone curse immunity slap on a 2x Vanberk card or 1x Vanberk and 1x Maya purple then either in middle or lower, your choice.
Shield = F.Knight/King* shield w/ GTB. Bring an Usakoring shield as well incase of fights.
Armor = F.Knight/King* armor w/ GR+TAO card or if you can GR+RSX. The 2 that I usually bring whethere it is PVP or MVP hunting
Cloak = F.Knight/King* cloak w/ 2x Skoll card. This would be enough for MVP hunting.
Shoes = F.Knight/King* boots w/ 1x D.Wiz card + 1x Green ferus or 2x Green ferus. I just usually use 2xFBH in case I get in a fight.
Accessory = 2x Str gaunt
Weapon1 = L.Sinxcrit w/ 2x TG + 2x Paper card is what I use. It is also an all around card set. But you can remove the TG and switch them w/ AK for pure MVP hunting
Weapon2 = L.Fenrir or L.Hels, I suggest L.Fenrir w/ the same cards stated above
*Donate or Vote
Thats just a basic guide though. Remember to EDP and enchant an element to your weapon. I hope you know your elements. Bring alot of seeds as well.