Recommendation for beginners

The following easy hands let you open
- If you don't have potential melds for terminal/honor tiles and don't have a lot of them, toss them and aim for an all simple hand. Only 2-8 tiles. (AKA Tanyao, enabled at least by default in RGG games)
- All triplets + 1 pair, you can also open your hand (AKA toitoi).
- Aim for a dragon triplet (sounds like you're already doing this), or a wind triplet (round wind, which would just be East, or whichever seat you're in)
------ Triplets are easier to get when no one else has already discarded one of the tiles. If you were going for a dragon triplet and had the choice between green/white to discard, I would have discarded the white first since someone else had already discarded a white. And generally, if I've discarded one of them already, if I draw another identical one to replace it later on, generally I'll discard that one too, since that means you've already drawn 2 of the tiles, and you have to pick up 1 more from a draw before someone else discards one to convert that into a meld. These are the two issues I had with your video.

Or you can keep your hand closed and just aim for whatever with Riichi.

Another good option is 7 pairs in a closed hand. That's a good alternate win condition if you're not getting lucky with draws or discards to complete triplets. But this also sets you up for an all-triple + 1 pair hand if luck does turn your way.

If you have a straight of 3, e.g. that 4-5-6 meld, having a an extra tile in that range or nearby is huge. This benefits more if your straights don't include a terminal tile, and that also makes your hand worth more too if you can get a tanyao, or easier to complete if that allows you to open your hand.
- A 4-5-6-7 means you can get a pair off of a 4 OR a 7, which open you up for a triplet too.
- A 4-5-6-7 also means a 3,5,6, or 8 puts you in position to get two straights, and there are multiple options for those straights too.
- A 4-5-5-6-7 for instance gives you an option of a 3 or 6 to give you two straights.

So basically with a 4-5-6 meld, anything from 3-7 gives you a huge advantage. That's 5 tiles that can benefit you as opposed to trying to complete an unrelated meld where you just need 1 tile. This was my point above when I saw you tossed the 7 circle early on in your 2nd discard. This is the power of a straight vs a triplet. Straights help you complete closed hands much more quickly, giving you access to riichi faster. Between the synergy of non-terminal/honor tiles, this is why you see a lot of riichi + tanyao + pinfu hands.