So, just got PoR for X-Mas and I'm loving it. Never thought I'd like a game that was just a string of battles, but it's great :)
I put it on hard my first time through, so obviously I don't do so hot all the time, and I was wondering which units I shouldn't worry about losing, because I get sick of restarting my Cube every time someone dies :P
Also, I guess it'd be good to list my units, eh?
Ike
Titania
Soren
Rhys
Shinon
Boyd
Oscar
Gatrie
You should reset when someone dies anyway. Anyway, you might want to hold of on using Titania, especially in the beginning.
Train Ike. Keep him safe at all costs. If you have to, unequip Titania and use her as a meat shield, or as a lure for Ike. Train Boyd and Oscar well too, they end up great. On promotion, give Oscar axes. Boyd will be a great front liner eventually, and getting bows helps him out a lot too. I've never trained Gatrie before, but he ends up good, according to average stats, so use him. Shinon's worthless. He's got the stats of a level 10 or so archer. Use him until he leaves though. You'll get him back later if you talk to him with Rolf and then kill him with Ike.
Rhys is a decent healer, but decent at best. Use him until you get Mist. Then cut back on using him as much, and train Mist as much as possible. When Mist is roughly level 15, ditch Rhys. Try to promote Mist and get her high level before chapter 27. Heal EVERY LITTLE BIT of damage. If it's one HP, heal it. She needs the EXP.
Rolf will come when you get Mist, too. He's a good archer once you train him, but it can be a death wish to use him too much in the start. Use higher level units to weaken enemies for Rolf to pick off.
Soren can be godly, but he can also suck royally. Give him a shot. Give him the same treatment as Rolf, weaken, then pick off. When he promotes (if you stick with him), give him staves. NEVER give a mage knives on promotion. They don't have the strength for them.
Later, you'll get Mia, a myrmidon. She can end up pretty good too, albeit fragile. She'll dodge well and dish out fair enough damage, and double just about everything. If you promote her quickly, she'll be one of your best units for a while.
You'll also get Marcia eventually, the pegasus knight from chapter 3. You get her a few turns into the chapter you get Mist and Rolf. Talk to her with Ike to actually recruit her. I've never used her either, but I've heard she's alright.
There's also a prison chapter. I'd advise you don't try to stealthily get through it, it's darn near impossible without a walkthrough. Unless you want to waste hours on it. You'll get a few units if you talk to some of them. Kieran, an axe knight, Brom, a knight, and Nephenee, a soldier. Give Nephenee Javelins and Vantage, she has Wrath when you get her. Watch her though, she might slip up sometimes. Eventually, switch to close ranged weapons as well for better damage, and a better hit chance. Killer Lance on Nephenee with Wrath and Vantage is deadly, by the way.
Kieran is difficult to train if you don't know what you're doing, so be careful with him. But, he is one of the better units. Great mounted unit. On promotion, give him lances. Keep him on the frontlines with Oscar.
You could get by with only them for the most part, but that alone won't fly. You'll get a thief, Volke, eventually. Train him if you want to use him as a fighter too, and try to get him to level 20 before chapter 19. Then in chapter 19, choose to take him still. He takes from your funds whenever he opens something though. Don't waste your occult scroll on him though. You'll get another thief too. His name's Sothe. Don't use him, he can't promote. Unless of course, you want to have a good data transfer Sothe to Radiant Dawn, then train him as much as you can, abuse BEXP for good levels, whatever. Use stat ups if you have to. Try to cap as much as you can, and you'll get FE9 Sothe's stats that you had in the data transfer for RD Sothe's bases.
Besides what I've told you, experiment. Some things I've said may not work out for ya, too. So really, mix it up a little. Take my advice and wing it at the same time, yanno?
Just to add, when Oscar promotes if you give him bows he can triangle attack with Boyd and Rolf, but it's not that useful.