When I started out on the Hellenistic path, I took to the web. I visited several forums, some of which were completely Hellenistic. It was a short visit to most of those; Hellenismos can be very fledgeling-unfriendly. Those new to the faith are warned that they must not perform ritual until they fully understand what they are doing, they must not... well... do a lot of things. It seems most of those 'do not's' are linked to hubris; the Theoi will punish those who perform Their rituals wrong, because the fledgeling practitioner thinks they don't have to study in order to approach the Theoi.
It's a nice sentiment, but I don't think it holds especially true. This is personal opinion, but it is based upon our basic societal and biological structure--the same one the ancient Hellens helped build: it's not hubris if you perform the rituals to the best of your abilities and the best of your knowledge. This includes having done your research, of course, but we all miss things.
Knowledge comes to us in bits and pieces. As we develop from babies into adults, we find teachers for everything. Like our parents did not punish us for doing something we could not possibly have known was the wrong thing to do, the Theoi will not either. This does not mean you can simply do what you will, call it Hellenismos and laugh at everyone for spending years researching mythology, ancient Hellenic culture and the classics.
Performing rituals incorrectly only becomes hubris when one knows the proper way of performing them, has made a commitment to performing them correctly, and still chooses not to. This is where the 'willful' comes in. This means I feel the Theoi frown just as much upon inaction when the practitioner possesses the required knowledge, as when the practitioner does perform ritual, but incompletely or half-heartedly. Consciously not studying so you can keep doing what you're doing is just as much hubris as performing the rituals willfully incorrectly.
What I read a lot on the internet is people putting their own needs before those of the Theoi. 'It sounds like a lot of work', 'I don't have time for that', 'I don't have room for that'. Modern religion allows those excuses. Within non-Recon Pagan paths, you simply adapt your practice accordingly. As Recons, we do not have that luxury. Reconstructionism requires a shift in thought from a me-centered practice to a Theoi-centered practice. This means you do the work, you make time, and you make room. Period. To not do so, is to commit acts of hubris, day in, day out.
I encourage any new practitioner to go for it. Read up on the basics, get your tools together the best you can and follow the basic steps--procession, purification, prayers and hymns, sacrifice/offerings, prayers of supplication and thanks. Keep studying and adjust your practice accordingly. If you discover you have been doing something incredibly bone-headed, offer words and offerings of supplication. Apologize for your error, explain you did not know any better and you will do right by the Theoi from this point on. Hold yourself to that promise.
We all make mistakes; there is nothing wrong with that. The willingness to learn and the ability to adapt accordingly are what staves off hubris and fosters kharis, the cornerstone of Hellenismos. Hellenismos is not difficult. It takes hard work and dedication, and the willingness to learn, but the basic practice is fairly simple. Once you get that down, you're set. Just go for it. The Hellenistic community can be a bit difficult to deal with, but there are a good few of us who are very nice and welcoming. Me included. Minding your actions to avoid hubris is very important, but it should never keep you away from honoring the Theoi in ritual.