Advice on Thieving
With thieving you really want to pick a target and stick with it to level mastery and eventually get to 99 for that +75. If youre able to get to the runic ruins you can farm the thief for a bit as he drops +50 stealth and -0.1s gloves. Astrology and agility also have boosts to thieving. Herblore also has a really good potion even at tier 3.
Anything that gives mastery is a huge plus. The leprechaun and owl synergy is amazing however it requires a ton of astrology and summoning levels so its not super needed. The ring of mastery is also good but again it usually takes a lot of fishing.
On top of being good for that npc the 10, 25, and 95 mastery checkpoints help out a ton as welland are pretty much required at the higher npcs. Levels will come in time but after you get your first bits of gear you really want to find an npc and stick to them.
My recommended order would be to farm the highest xp npc until you get to the bandit hideout and goblin chief (it may be worth spending a bit on the gloves if you dont have the ones from thieving to make this go faster).
The goblin chief grants a head that is best for leveling and the bandit hideout has an area drop cape that is gonna be your go to until you get the skillcape, so farm a single npc there until you get that.
Once you have those two pieces depending on your skill farm the highest xp/hr npc (which could be either the newest one or the highest mastery one depending on your success chance vs the xp they give) until you get to Bob the farmer. Bob is the first npc you want to get to 99. Id spend all your mastery point to level him as high as hell go and then farm him until you get to the acolyte, which takes a while.
Bob drops almost every seed youll need for leveling farming, strawberry seeds which you can use to make thieving potions, and bags which make helpful consumables. When farming him you should also get the sneakers if you havnt already which helps stealth quite a bit.
The acolyte is my recommended for the next npc to farm at 99 as they drop the book of scholars which helps leveling any skill a ton. From there just get to level 99 for the very nice skill cape. To farm any higher it is almost required you have astrology, agility, and herblore buffs.
Farm the explorer as he will eventually drop a grappling hook and pants for thieving if you have the expansion. Thats what I found to be the best path to get all the gear and level for thieving.
Also its important to note DR affects the hits from thieving so just equip your highest dr gear in each slot that dosnt have thieving gear on. Also the dr prayers do work and dont consume any points.