As this is the tutorial chapter, most of the battles are straightforward. Naturally, the toughest mandatory enemy in this singularity is Altria Pendragon (Alter) fought in the last section of the singularity.
Tips and Tricks
Altria Alter is fought alone
She has the highest HP for enemies you have fought so far, but the battle against her usually remain straightforward
Since Altria Alter is a lone Saber, it is most recommended to put in an all-Archer team to take advantage of the Class Weakness
This battle can be made even easier if you managed to summon EMIYA during the Tutorial Summon.
If you spent money and managed to get Atalante (she's not part of the Tutorial Summoning), she can be useful due to her higher starting stats in this early stage of the game.
While she is not bringing class advantage with her, Mashu Kyrielight can be a good Servant to bring in case Altria Alter unleashes her Noble Phantasm, in which Mashu's own NP can reduce its damage. Remember that right now you are probably lacking stats and HP, so Mashu's NP will be useful!