Take this as constructive criticism. I play my line really aggressively so if you find your self squishy 1v1 at low levels you do something wrong. Take Rampage on level 1, Devastating Charge on level 2 (this is awesome opener and if you want to get into safe zone or attack ranged without losing 30% HP in your running to him, learn Spirit of Dread at lvl 3. From here on follow priority: Onslaught of Shadows -> Rampage -> Spirit of Dread -> Devastating Charge. There are some bad items but if you give effort to play Hecarim and test more builds you will find some better options. Going for full ad and ignoring attack speed would suit you better as Rampage will do your dirty work (it scale with cd reduction extremely well and you can get following numbers 2.4sec cd after first, 1.8 sec after 2nd hit and 1.2 sec from that point 190 + 0.6ad (300+ late game if you build right) mean you hit apx 370 aoe damage every 1.2 sec for next to no mana.