There isn't any one skill you can train to RuneScape gold be a good one. Each of them is useful to some extent, and the only thing that training one will do is hinder you in the long term. However, here are some suggestions and the reasons behind them:

Construction. One you can have a portal room as well as a menagerie and a prayer altar, this becomes very beneficial. The portal room can be extremely useful, particularly when you're beginning your journey as a member and most of the teleports that you'll need are located there. The POH is also great for storage, it holds almost all tools, books, as well as lots of other clothing and armour.

Agility can also be very beneficial and achieving it at least 21 is essential to ensure that you can utilize the Varrock-Edgeville shortcut. And getting more advanced is very helpful for battling monsters, large quest areas, and even PKers (true experience here). Achieving it to 21 should be among your first actions to try to do.

Summoning is a fantastic skill, but you can't do it immediately. If you've not already done so done so, get 43 prayer by using penguin points and the Troll Invasion DnD, and then put those points into summoning. Being able to gain the Spirit Terrorbird (level 52) is extremely useful and beneficial. What I'm trying to say is...always make sure you are able to attract your charms. It's not worth letting them on the ground.

Farming can be helpful for herbs however, you should let that slide for a few days. It's definitely not the most important thing that you should not ignore. Learn to farm and increase it gradually. By the time you're at level 30/35, it's likely that OSRS Membership For Sale you' be able earn fairly regular cash from it.