Here we are. A card I really don't want to review. Why? Basically, this card is a bulk rare or a $3-$10 card and it all hinges on how good Manifesting actually is and how many decks want to take advantage. This reminds me a bit of Luminarch Ascension which was a few bucks because one deck built around it and used it very well but not every deck was able to take advantage of it. Is the lifegain something decks need in Standard? Is 3W too much to pay for a 2/2, even one with upside?
Yesterday, I gave a pretty "meh" review of Wildcall and a few people, including one in the comments section of the article said I was underrating the card. I think it all hinges on whether we want to invest an entire card to manifesting. I personally think the incidental manifestation you get from a card like Whisperwood Elemental is fine but I don't know if I want to use a whole spell to get a 1-shot Manifest.
This is a bit different, though, letting you Manifest repeatedly, and every time you put a creature you can afford to flip up into play, you can potentially gain some life.
I'm inclined to say this is pretty good, and if I underrated Wildcall, I'm probably underrating this a bit, too. In a control deck, this is a good way to get creatures into play when you need them and gain some life to put your life total out of reach. However, you'll need to be playing enough creatures that you can flip some of those permanents up that you manifested, so it's not going to gain you any life if you are a pure control deck with few creatures. You can still use it as a Mobilization. though, so maybe it has merit. This is a hard card for me to review knowing I lack knowledge of the future. I will say this.
If this sees fringe play in control decks, decks which can't really maximize its use due to the few chances to get the lifegain trigger, this will be $2-$4. If you think it fits best in that role, that's probably your price target.
If people decide Manifest is too risky in a deck with a lot of spells, 4 mana is too much for a token or a better card in this role comes along, this will be bulk.
If lots and lots of decks are using this and the lifegain causes really annoying mirror matches and this is the primary way people put creatures into play, this could be anywhere from $6-$20. If you think this card is that good, it's a $10-$12 playset on eBay right now and you have room to profit. Personally, I'm staying away.