As commenters have said, there's no way to decide what "fixes" to apply without knowing what "defects" exist in the recording.
In my home studio, there is only one "effect" that I might apply as a matter of course to microphone recording of vocal tracks without much regard for the source audio or the context of the rest of the mix: A high-pass EQ (low-frequency roll-off). All but the most profondo of bassos produce little below about 80 Hz, and the roll-off removes a lot of unwanted urban (e.g. railroad locomotive rumble) and building mechanical (e.g. ventilation fan motor) noises.
Everything else should be considered only in the context of the particular singer, material, accompaniment, acoustics, and desired mixing outcome.
Your choice of interface doesn't make much difference in this setting. Any difference between the Scarlett Solo and a comparable product (or earlier generation of the same product for that matter) is likely imperceptible in your application.
I don't know your microphone firsthand, but I see from the product specifications that it is switchable between omnidirectional, cardioid, and figure-8. How have you been using it? Cardioid is probably your best choice for a single vocalist not far from the microphone, but note that this pattern will have some proximity effect, increasing low frequencies on nearer sources. How to use this depends on your desired outcome.
I see that your microphone has a switchable 80 Hz high-pass filter built in. It's best to use it there where appropriate (rather than with an EQ plug-in), because at the microphone, it can remove unwanted low frequencies before they have a chance to use up your preamp's headroom (and by extension, your recorded audio's resolution.)
As for acoustics: You probably have many issues in a completely untreated room, including most importantly:
- Comb-filtering caused by reflections. This causes strong peaks and valleys in the frequency response that vary with small changes of the position of the microphone and source (singer) with respect to the walls, ceiling and floor.
- Standing waves which cause the bass frequencies to pile up or cancel out at certain locations in the room. Search online for room modes calculators to see which frequencies are the greatest concern in your room.
- Assuming you are listening in the same untreated room, you are unable to accurately judge the recording you have made, which leads you to believe all kinds of corrections are necessary. Caused by both the issues above, and highly dependent on the position of the listener and monitors with respect to reflective surfaces.
I suggest you learn about acoustics and treatments. (As a starting point, try some of Ethan Winer's articles like this: Acoustic Treatment and Design for
Recording Studios and Listening Rooms)
If you improve your recording and (especially) listening environment, you'll better be able to trust your ears to decide whether signal-processing corrections like EQ are needed, and which ones.
Unless you are a broadcast engineer, dynamics processing (e.g. compressors and limiters) are primarily an artistic choice not a corrective one, and thus dependent on style. One exception might be when you're stuck with an irregular vocal take, and you can't fix it with automated track gain. Either way it's not something just to apply all the time.
A de-esser (really a special form of dynamics processing) should also only be applied if it's really needed and a better take of the vocal is not possible. There are dozens of online articles covering microphone techniques to avoid sibilance.
Lastly: Don't wear a hat.