You should read my suggestions in various farming threads among this section of the forum. I highly suggest starting over and farming atleast SOME amount of sp. You have no idea how much easier it is to farm and then move on with the game.
I know that you don't want to give up your current char, but to be honest with you, if you want to be serious about SRO, restart. I can get to lv 18 without ticket in under one day of playing and in like 4 hours of lvl'ing in that day. So attaining lv 20 isn't really that difficult or time consuming.
http://www.silkroadforums.com/viewtopic.php?t=20299
I think it was in this thread where I suggested my way of farming. If you can't get your hands on a SoS 16 bow, then just use a 3-5 lvl gap and play the game like that. Zero gapping the game without farming is next to impossible. Zero gapping only allows enough sp for 2 trees with limited skills within them. You won't be satisfied with your character build and you'll hate SRO because you can't compete with everyone else. So my suggestion to you, is to farm atleast SOME sp. Having 2 sp at lv 20 is seriously depressing.
To answer your questions, using sp will just allow you to upgrade or attain skills and masteries. If you don't have enough sp, obviously you can't compete as well as others who have sp to lvl up everything. Lv 70s with 0 gaps obviously will do better than lv 70s with a 5 gap. But that's not the point! You don't know how crowded the caves are when you get to 64+. Aside from competing with others for mobs, mobs don't give 'enough' sxp for you to get enough sp for skills. To upgrade a lv 60+ skill or mastery, it costs in upwards of 1k sp.
I might as well say this and don't take this as a dis or anything, but this game is difficult. The grind is absolutely horendous as you get to lv 57+ w/o item mall help. The difficulty almost resembles an exponential curve. Just wanted to give you a fair warning before you get a real chance to whine about the game
