Greetings and welcome, sir! You should definitely feel free to play whatever haracter appeals more to you, but also know that Tira isn't the most beginner-friendly character around(that "Ease of Use" stat on the character select screen is fairly accurate). She has a lot power, but unleashing it is difficult for a few reasons.
1: No mixups whatsoever. This means you need to really study your foe and get in their head to figure out what they do in various situations so you can get them off their feet and into a position you can really put the hurt on them. The only mixup tool Tira has(JS 44AA/JS 44A2A) is so bad you're better off using it once every...hundred matches or so. It's that bad and it really only has one followup, which you need meter for at that.
2: Those wacky persona shifts. These will both limit and extend your combos depending on which attacks they occur on and how much meter you have. As a rule of thumb, when you have meter(say 1.5 bars), you want as many persona shifts as possible. Usually you can get more damage in Gloomy(GS) by gambling the odds and using moves with a chance of persona shifts attached to them, or you could play it safer and do less damage without the odd chance of persona shifts in mid-combo.| Also, the 40% health "rage" shift can be quite a bother. For the most part you're going to want her to be Jolly(JS) just before this happens so she'll end up going Gloomy when it happens. If you're in Gloomy and nearing the low health range, you can usually switch to Jolly just by ussing 77A: this move has a high chance of reverting to Jolly.
3: Mediocre punishment and range. Sub-par in punishment and essentially average in range, baiting whiffs is difficult with her range and Tira can't really outrange anyone but Viola most of the time. Usually if you block something and your foe didn't use a move with little pushback, your punishment options may be limited to low damage pokes. What you want to do is try to bait a whiff and knockdown or launch your foe so you can get a combo of tech trap. Try limiting your sidesteps for awhile and then doing a Quick Step in GS 33*99B for launch to whiff punish a vertical, as an example.
4: Significant weaknesses in both Jolly and Gloomy personas. Jolly has sub-par to terribad frames on just about everything, overall low damage output, and much weaker combos(without persona shifts) than Gloomy. Gloomy obviously has that fun self-inflicted damage, many of its best moves may shift back to Jolly, and a much more narrow stride(meaning every step she takes covers a smaller distance; which can be problematic when trying to step around attacks).
There's plenty more and this is all just in the experience I have, there's plenty more-skilled Tira players here than I that can you tell you better ^^
