From what I've experienced in the game so far with the items and stats. Panties are a lot more important then you think. They protect you from sexual attacks on your private parts which makes the enemies hit you instead which is a lot better then receiving a sexual attack that will lower your accuracy drastically.
A early game tip would be to grind levels early on to like level 3 or 4 before you reach the next checkpoint since vit stat really makes a difference in reducing damage besides quick being the key stat in having extra moves, avoiding traps and attacks. Levels make a huge difference. I tried doing area 20+ at level 1 and completely failed and probably would of been able to do it if I hadn't decide to reset my orgasm counter as I was level 10 instead.
In terms of costumes, China dress seems to be the best since it gives the most quick stat while also providing strength and a little vit stat.
Miko clothes is good against sexual attacks, but you are better off doing more damage with China dress.
Bunny costume does give a second highest quick and makes your sexual attacks stronger, but I honestly don't recommend it.
Magus costume does give you a significant boost in magic damage, but your quick stat will tank which is a awful drawback.
Tentacles clothing are a big no, only use if you want to be sexually attacked over and over due to -20 quick. Don't even have them as there is a trap that makes you wear them.
For items, any passive items that give a stat boost are automatically good. Game changing items that I found would be: Angelica statue and Vaginal Speculum.
Angelica statue gives a tremendous boost in damage if you don't wear clothing. you can go from doing a measly 50 damage to like 250 damage at like level 1, it will allow you to one hit a lot of mobs with just your fists.
Vaginal Speculum makes it so all sensitivity goes to the uterus which might seem bad, but actually it's really good, your character won't be stimulated in multiple areas as much which means your sensitivity increase will drastically decrease. I tried using sex toys with it on and it took significantly longer to have an orgasm.
For weapons, there are 5 types: ranged, spears, two handed, one handed, and boomerangs.
I find boomerang type weapons to be the best, being able to hit through walls is really handy since enemies don't smartly follow you. They also hit enemies twice which helps you either kill the enemy in one go or allow one miss and the return hit kills.
Ranged weps are good early on, but it's hard to find ammo so better to discard once you use up the ammo.