Updated Version of My Question: Need Help With Decision Please! :( IVs Included

Hey there!
Don't stress too much about getting the perfect units. Good units can serve you well far into the game, and by that time you'll have some great units. Pass on rerolling.
Cavalry teams are a great way to start, and you can make a budget one pretty easily, considering you have Brave Lyn and Sigurd. I think your Sigurd might not be +Res, since Divine Tyrfing gives +3 to Res. All you need are some Gunters and Jagens, which can be found at 3* and 4*.
Cecilia is a great budget green mage for cavalry teams. A 3* Nino can be used to give her Gronnblade, and the cavalry buffs will alow her to do lots of damage. I don't want to take up too much space, so see the cavalry team page on this website for more information.
The blue slot can be occupied by many different units, but Reinhardt can be summoned at 4*, and is still one of the best units in the game. Dire Thunder is extremely useful, and it just gets better if you have a 4* Klein for Death Blow 3. Check the Reinhardt page for more.
New Years Azura is very good, but you should think about your semi-long term plans for the game if you will be playing for some time. Saving orbs for the perfect banner is normally what I do. If you can't be that active, just logging in every day helps because there's almost always a login bonus, and being more active allows you go complete quests for even more orbs. Unless you need perfect ivs or 1 specific units, all the free orbs in the game are enough to make a great team. I'm FTP myself, and have 58 5*s.
Hope this helps! :D

If you're going to be F2P, you'll never get every unit. It's a fact of life in the game. Even when you get a unit you want, they may have "bad" IVs. However, in my experience, "bad" IVs mostly matter at the top levels of arena play. Once you upgrade the basic "A slot" (+Att, +Spd, +Def, +Res) sacred seals you can patch the "bad" stat with a seal. This means all the units you pulled can be useful.

In two weeks there will be a new banner and a new "must have" unit. You can't worry about not getting a good unit.

I agree with the previous post. If you're just starting, and with the units you pulled, build a cavalry team. Sigurd is a great unit, and Brave Lyn is probably the best unit in the game. Save your feathers and level up Cecilia. Give her bowbreaker and she can counter Reinhardt and Brave Lyn, which you'll run into all the time. Give your cavalry team Hone/Goad buffs and Reposition/Draw Back assist skills and you'll be able to get to tier 18/19 of arena.

That being said, f you feel like testing your luck, create a new account and see what you get. If you like it better switch. You don't really have that much invested in the game yet. The only unit you'll likely never get again is Winter Chrom (who is a very strong unit).

If you're worried about Orbs, IS is pretty generous. If you login every day and complete the quests etc... you'll get 250-300 orbs a month.

Don't worry too much about getting perfect IV's or units, especially when you start. Sigurd, Fae, Brave Lyn Christmas Chrom and all really solid units. Once you start playing for longer, you'll begin to get better and better units and be able to inherit skills to be able to make your strong units even stronger. There's also plenty of great units which come at 4 stars, which you can unlock potential for. I personally recommend Nino, Effie, Cherche, Soleil, Nowi, and maybe Olivia (It's always good to have a dancer, even if Olivia isn't the best one). Basically, the point is not to stress to much and have fun eventually getting stronger. As for worrying about orbs, i'm F2P as well, and though there are occasionally dry spell where orbs are in short supply, I'd say that if there's a unit you really want, try for them. Don't worry about hoarding orbs in case there's a better banner later, since you'll always be able to get more.