While on your journey in Albion you will find three special potion types, "Ages of Might", "Ages of Skill", and "Ages of Will". Each of these potions offer 1,000 experience points multiplied by your combat modifier. If your combat modifier is 20 and you use one of these potions, you will gain 20,000 to 21,000 experience points in the respective class. If you do not have a combat modifier at the time of ingestion, you will only receive 1,000 experience points. You can also find three food items, "Red Meat", "Carrot", and "Fish" (not Moonfish). Each of these food items can be bought at Market Traders, and each will give you 3 experience points multiplied by your combat modifier. If your combat modifier is 1 or lower, you will only get the 3 experience points. Eat "Red Meat" for Combat Experience, "Carrots" for Skill Experience, and "Fish" for Will Experience. Eating these in excessive amounts will cause your character to gain weight. Food items are a good choice if you do not care about your character's weight. You can save the Ages potions for times where your combat modifier is high.
When you defeat Jack Of Blades for the first time, you will get the Sword Of Aeons and a lot of experience gems. Let the sword regenerate your health, then Hero Save and load the game. Do not kill your sister or throw the Sword Of Aeons in yet. You can kill her or throw the sword in later. You will have all the experience gems you earned for defeating Jack Of Blades, and you can use them to upgrade yourself before you fight him again.