Need help with int gear

Cheapest way would be to just add 36 int, you can just wait to obtain the NX again to remove the int.
If you're looking a way to stay 4 int, it really depends how early you want to be able to reach 40 int imo.
For example
Level 20+ opens up bathrobes
Level 35+ opens up racc mask
Level 50+ opens up yac, zhelm, deputy

Another way is to try your best to get tier 1 ring out of the way (this takes a lot longer).

Very basic items that don't cost too much would include
a wand (saw some 6 ints for like 4m)
A basic maple bandana (saw some 3-4 int blue ones)
Getting the slime shoe (2 int, but needs level 30)
Making some simple earrings (scrolls cost maybe 1m each)
Making a low level cape (scroll cost maybe 1-2m each, level 25 required)

 

Step 1roll 5/5/10/5
Step 2 only int until lv 4 (you need 35str)
Step 3 from 10 to 35 only int (150)
Step 4 wash each lv until you reach max health at lv 124
Step 5 tank the Bigfoot and use only power guard,good luck brudda

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Best hp wash guide

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10 int cape is very good value. Might cost you like 15m for a low level one though. Ive seen 10 int YACs for like 10m.

5 int earring is also very cheap. Probably less than 5m.

Then there is the scrolled wand. You can probably get a +6 int for 2m or less. You can also try to scroll yourself. Wand 60% is like 100k.

A +2 int red marker clean is like 1-2m.

That will put you at about +23, all equips are low level and cheap. The rest of the stuff can get pretty expensive from here on out. Low level int hats get expensive very fast.

Some good choices would be a 10 int bathrobe (probably cost you like 20m), and a monster book ring (1-10 int).