[Divin12]

PHP Code:

#include <sourcemod>
#include <cstrike>
#include <sdktools>

public void OnPluginStart()
{
    if (GetEngineVersion() != Engine_CSGO)
    SetFailState("This plugin is only for CS:GO !");

    HookEvent("round_start", OnPlayerSpawn);
}

public void OnPlayerSpawn(Handle event, const char[] name, bool dontBroadcast)
{
    new firstct[MaxClients + 1], firstt[MaxClients + 1];
    new i, j;
    for(i = 1; i < MaxClients; i++) 
    {
        if(IsClientInGame(i) && !IsFakeClient(i)) 
        {
            new iTeam = GetClientTeam(i);
            if(iTeam == CS_TEAM_T)
                firstt[i] = CS_GetClientContributionScore(i);
            else if(iTeam == CS_TEAM_CT)
                firstct[i] = CS_GetClientContributionScore(i);
        }
    }
    for(i = 1; i < MaxClients; i++) 
    {
        for(j = i+1; j < MaxClients; j++)
        {
            if(firstt[i] >= firstt[j])
            {
                firstt[j] = 0;
            }
            if(firstct[i] >= firstct[j])
            {
                firstct[j] = 0;
            }
        }
    }
    for(i = 1; i < MaxClients; i++) 
    {
        if(firstt[i] > 0)
        {
            GivePlayerItem(i, "item_kevlar");
        }
        if(firstct[i] > 0)
        {
            GivePlayerItem(i, "item_kevlar");
        }
        
    }
} 


This is for first from ct and first from t, not tested, test it and check if it works.