If I were starting, a 6.5 caliber would not be where I would start.
If you will be happy staying in the 1200-1500 fps range to start it will be easier. But small rifle bullets are tougher, and the faster you go, the tougher it gets.
My suggestion is to start casting for a .38 or larger cal pistol. That will help you get your process and technique honed while making serviceable bullets. It will be frustrating to cast bullets that shoot patterns. If you cannot cast decent pistol bullets, it will be unlikely you will be successful with rifle bullets.
Lee molds are cheap but if you get poor results will you blame the mold or you? Buying a "good" mold takes a bit of the doubt out.