Which Wedgits are most Wonderful? That would, of course, depend on how they will be enjoyed. But I think I finally have a recommendation for perhaps the majority of cases, and certainly what I would recommend as a gift if I had no further information about the recipient.
For Part I, I recommend the Starter Tote: it is a great set of parts with a great deck of design cards - and for now at least, the only way to get this specific design deck is in the Starter Tote. The Tote itself is large enough to carry the additional pieces and cards below, as well as an extra Junior Set to build the Deluxe set designs in the 100 Advanced Design Cards deck, if you go that direction.
For Part II, I recommend the Xtras Design Cards and Stix: this includes what I now believe is the best, most fun set of Wedgits design cards yet, along with some nifty extra parts which combine very well with the Starter Tote parts to allow building most of the designs in the included Imagination Deck as well as all Junior Set designs (design deck available separately).
We may be a bit confused here, but please stick with me. I think it will make sense in the end. One thing that might not make sense is that none of today's pictures were taken with that recommendation. Instead, they are all Mini Wedgits, though the designs all were built from the Imagination Deck, which is a key element of my recommendation.
In fact, I started with this deck and worked backwards to create my recommendation. Since the deck is only available in the Xtras Design Cards expansion, the parts included in that provided some direction. The Starter Tote provided most of the rest of the parts needed, including the building board, and including another very nice deck, not otherwise available at this time.
Not all the parts. But this is not critical. It would appear that the three Stix with the Xtras set were a late addition, and most of the designs only use the three Stix that come in the WEDGiTS Imagination Set. Some also use the parts that come in Xtras Building Board expansion. With the Starter Tote plus the Xtras Card set, you have all those pieces, plus all the pieces in the Junior Set. All you are missing are the extra Stix in in the Xtras card set, which are only used in a few designs. Buy an inexpensive STiX set when you decide you need them - that'll even give you extras. For creative play.
Sample designs, in whatever form, provide instruction, inspiration, and challenge. One does not need to have every piece to build a particular design for that design to still provide benefits - in fact it may better encourage creative play if the constructor is required to build something similar rather than identical.
I describe this as a two part recommendation because they make a good two part gift - the Starter Tote, with plenty of pieces and design ideas (all buildable!) to get started, and the Xtras Design Cards and Stix set to take Wedgits block play to another level of challenge and entertainment. From there, go on by adding other sets, other decks, or filling in the missing pieces - the Wedgit player will have enough experience to know which way they want to go.
When I started playing with the Xtras Design Cards and Stix, I found myself laughing as I finished one design and hurried on to the next - not something that usually happens. The other decks give satisfaction, pleasure, enjoyment - but not laughter. Hence this recommendation.
Good Block Play.
Footnote - it is a little harder to do the Imagination Deck designs with Mini Wedgits, as in these illustrations - but not so much in construction as in which sets to buy & how to pay for them. Start with the Dog Set and Frog Set for the Stix. Many places that a Jumbo Octahedron is called for, a standard size Octahedron can be substituted without penalty - one of the images even has one in a structural position. The eXPANnie Set provides Jumbo greens and one Jumbo Octahedron, the Owl Set would provide more Octahedrons. My Mini "building board" for now is just 25 greens pushed together.
Disclaimer - My Xtras Design Cards and Stix set was provided as a sample by the Wedgits folk - I had intended to buy but hadn't found one yet.