From level 1 all up to level 28, you will need OSRS gold to use Darts or knives to improve for your Ranged level. Those may look kind of expensive at first, but you won't need too many to advance your level. They're very accurate and hits , and are available at Grand Exchange.
Always use Knives over Darts since they're superior but if you're not able to afford them, Darts are an acceptable alternative. Beginning, you want to start with Iron weaponry and switch to Steel at level 5. At level 20, you can equip Mithril Knives. Keep those until level 28.
Level 28 grants the ability to carry a Dorgeshuun Crossbow, which is an awesome weapon at this moment. It's powerful in hitting as well as accuracy and costs almost nothing. Bone bolts that can be shoot by this kind of bow are extremely cheap (around 6 cents per bolt). However, this isn't all you need to know - you can also put Godbook or Shield as a second weapon because it's a one-handed crossbow. This makes it the perfect weapon for training until you reach level 50.
While Dorgeshuun Cbow is a great weapon for buy OSRS GP leveling at this stage but you might want something different. If you're willing to risk some money and need a different weapon, you can try traditional crossbows. Level 31 Steel Cbow/Bolts for 36 Mithril Cbow/Bolts and after that, 46 Adamant Cbow/Bolts. Although they have better bonuses than Dorgeshuun they are priced higher. The price of Adamant Bolts on the Grand Exchange right now is currently 30 times higher than the cost of Bone Bolts making the use of the Bolts a significant waste of money.