I started playing Runescape in early 2005 and have returned several times after several fractures. Nobody ever truly stops playing RS gold and they're lying to themselves, if they say they have. Is membership worth purchasing at low lvl? There's no'correct answer' and it depends on how you play the game. How long are you spending on the match? How much money are you making? How fast are you skilling? There are several questions before determining the reply to your 16, that you need to ask yourself.
If you just devote a small quantity of time around the sport you need to generally wait until mid/high levels to subscribe to membership. With each skill level you achieve, the and tougher it becomes to progress to the upcoming levels. P2p generally permits you to acquire quicker xp (especially after you progress through the levels). In other words, levelling up is quite simple to do at reduced levels for f2p (and p2p alike) but much harder to perform at higher levels (particularly for f2p). As a result of this, it is usually recommended that you work your way through the noob positions as f2p and upgrade from the selection.
My personal advice is to get membership at lower rates if you intend on playing a lot (several hours/day) or waiting till mid or large levels if you play frequently. In the case of the latter, attempt to 1) Aim towards finishing most (or all) f2p quests, two ) Reaching lvl 40+ at many (or all) f2p skills, AND 3) Accumulating - at the least - 1mil gp before buying membership. However, you still haven't purchased membership and when you have already achieved all of them , then you are losing out by continuing to perform f2p. Skilling and money making are much easier on p2p and you have access to hundreds of quests. So no matter what kind of player you are, it's surely worth it to buy RuneScape gold have membership in the long run.