If you're going to take the risk of self-piercing...
You're already saving a ton of money from being pierced in a shop-- you MUST buy properly sterilized needles and tapers from a reputable company. You MUST use titanium or real gold jewelry. Sterilize your environment properly.
Mystery needles from Amazon are not safe. Surgical steel is not implant grade or safe for healing piercings.
Use correct aftercare. Look at APP guidelines and other piercers' advice about anatomy/placement/max piercings per session or area.
I think self piercing is awesome, but it also has the potential to give you a horrible infection that will cost significantly more to treat than a professional piercing would have.
There's a reason why actual professionals never use stainless/surgical steel in piercings, why they don't do 12 tongue piercings in one session, why they have autoclaves and don't reuse needles.
This isn't 1980--you have a wealth of useful info online!! Do test piercings on different materials and _do not reuse the needles_.