Just don't forget to buy a chip for automatic item pickup from Devola and Popola as soon as they move into the camp later on. It's incredibly convenient, and if you advance the plot beyond a certain point, you won't have another chance to get it from them until near the very end of the game.
But yeah, there's no real punishment for experimenting with your ability chips as long as you don't get overly-enthusiastic about fusing them and end up with ones way too big to equip. Remember that the size of the resulting chip does depend on the size of the ones you fuse, and most chips come in various sizes even for the same level of bonus. But you can get some huge boosts from fusing them together, so it's a balancing act. And you can remove any elements of the HUD that you don't need in order to get slightly more room, but removing the OS chip means instant death, so don't touch that one (or do, I'm not your dad). Do buy the capacity upgrades as soon as you can, though, because they help significantly.
Eupho Guy is totally right, though: Auto Heal and Shockwave are available pretty early on, but can be some of the most practical chips in the game if fused enough times to get them to a high level. Combine Auto Heal with Deadly Heal and you're pretty much immortal if you play smart.
Oh yeah, and it's possible to go the entire game without even knowing about him, but (MINOR SPOILERS) there's a second weapon merchant in a secret room in the castle in the forest area who can upgrade your weapons to the maximum level of 4, as opposed to the regular one who can only go up to level 3. Level 4 weapons get extra abilities (like increased attack power when at maximum health, or automatically charging up power when not attacking), so they're worth gunning for.
Last thing (and more MINOR SPOILERS): If you have any sidequests you want to complete in the first chunk of the game, do them BEFORE going to the mission at the coast. Once you finish that bit, it's a point of no return for most of the sidequests.