It's not about showing something or ploff or trying to look appeasling to others, but about making myself feel great.

However, I don't like to do all my nails.

可以说I don't like having all my nails done

My favorite choice is only getting only the two index fingers done.

So as you can imagine, I wasn't the most popular customer at the nail salon.

That's like me getting 捏脚 when I have one leg? lol

I bought some press-on nails online and put them on my nails, and they could retaistay on for over a week.

It's much more convenient and within the low-budget, and I can changego through several styles in a month.

The only problem is that I might waste most of the press-on nails, because I only use those for index fingers, while they are sold as a set.

It's not about showing somethingoff or pleasing others, but about making myself feel great.

My favoritepreferred choice is only getting only the two index fingers done.

1. It would sound more natural to say you have a "preferred" choice.
2. The word "only" can be both an adjective and an adverb, and the general rule is to place it immediately before the word you are modifying. In this case, you're using "only" to point out which fingers are being painted. Here are some examples to make it clearer:

When used as an attributive adjective, we place "only" before the noun.
"There were three types of juice, but I tasted only the peach juice."
"I have ten fingers, but I painted only two of them."

When used as an adverb, we usually place "only" before the verb we are modifying.
"I tasted two juices, but I only sniffed the third."
"I trimmed all of my fingernails, but I only painted two of them."

Recently, I found a better ideaway to decorate my nails.

I bought some press-on nails online and. I put them on my nails, and they could retain(lasted / stayed on) for over a week.

Breaking this up into multiple sentences is optional, but makes it easier to avoid a run-on sentence.

It'sThey are much more convenient and within the budget,, fit within my budget, and allow me to change styles several times in a month.¶
(OR "They are much more convenient and affordable, and I can change styles several styltimes in a month.")

It is unclear what "It's" is referring to. Use the plural "They are" if you're still referring to press-on nails.
If you're switching back to referring to "a better way of decorating", you could say "This option is much more convenient..."

The only problem is that I mightay waste most of the press-on nails because I only use those for index fingers while they are sold as a setthey are sold as a set and I use only those for index fingers.

1. May vs. Might: In everyday speech, native English speakers use these two words interchangeably. Speaking grammatically, it is generally correct to use "may" for things the present tense and things that are likely ("I may fail the test because I didn't study at all"). It is generally correct to use "might" for the past tense and things that are unlikely ("If I get really lucky, I might still pass the test.")
2. See the above guidance for using "only" as an attributive adjective.

It's not about showing somethingoff or pleasing others, but about making myself feel great.

So as you can imagine, I wasn't the most popular customer at the nail salon.

I bought some press-on nails online and put them on my nails, and they could retainstick for over a week.

It's much more convenient and within the budget,; I can change several styles in a month.

If you're writing 2 sentences together without conjunction, you're supposed to separate them with semicolon.

It's not about showing somethingoff or pleasing others, but about making myself feel great.

However, I don't like to do all my nails. (or: I don't like having all of my nails done.)

My favorite choice is only(or: My preference) is getting theonly my two index fingers done.

I bought some press-on nails online and put them on my nails, and they could retain for over a week. (or: they last for over a week.)

It's much more convenient and within themy budget, and I can change between several styles in a month.

The only problem is that I might waste most of the press-on nails because I only use thosee ones for index fingers while they are sold as a set.

It's not about showing somethingoff or pleasing others, but about making myself feel great.

My favorite choice isI prefer to only getting the my two index fingers done.

Its grammatically correct, but I changed it to sound more natural

Recently, I found a better ideaway to decorate my nails.

I bought some press-on nails online and put them on my nails, and they cwould retmain for over a week.