一些

一些 points to a small, indefinite amount, while 很多 points to a large amount. If you bought a normal shopping-list amount, 一些水果 sounds fine; if you bought a truckload, say 很多水果. Use 一些 when the exact number does not matter and the pile is not huge. “我买了鸡蛋、面包、牛奶，还有一些水果，这些都是你和我的吃的和喝的东西，还有给我们的小猫和小狗吃的东西。” (I bought eggs, bread, milk, and some fruit.) ── [《吃的东西和喝的东西》](/read/buying-food-drinks#s10)

一些 treats water as an indefinite portion, like a bottle or jug's worth. 一点 focuses on a small amount, like a sip, splash, or spoonful. If you just want a tiny drink, 一点水 sounds more natural than 一些水. If you're setting aside a general supply, 一些水 is fine and means some water.

一些 sounds best in positive, open-ended statements where you are adding something. In a plain negative, it can sound like you are denying a specific 'some'. Chinese usually says 我没买水果 when you simply did not buy any fruit at all. If you need a soft 'any' in everyday speech, 我没买什么水果 works better than 我没买一些水果.

You do not add 的 after 一些 just because English says 'some of'. You normally say 一些人, 一些水果, or 一些钱 with no 的 in between. If you mean 'some of my friends', say 我的一些朋友, where 的 belongs to 我的. The 的 is not attached to 一些; it is attached to the owner.