I dont know if you purchase silk at all, but the premium plus after you do the three fruit quests gives you a total of 30k skill points, and allows you to instant log on and level faster. If your a slower grinder (solo, or just do like 3 hours a night) you can get all three quests done easy. So if you use 3 months of pt plus, that is 90k sp no matter what your gap is.
On Nivlam from lvl 0 to 90 with a 2 gap you gain 334,514 skill points, this allows you to lvl the faster and for a person whom only grinds 3 hours a night it would take about 8 months to get to 90 from lvl 0. So you have 334,514 sp from just grinding and 8 months ticket(30k x

240k from fruit quests. That equals 574,514 with a 2 gap. That is pretty painless, your only left out of your 700k goal 125k which could be farmed at ongs, or an increase in the gap for a few lvls at later in the game when you have more hp/def and drops are worth more.
*edited* spelling