Your implement bonus to spell attacks is always +1 greater than base (minimum +1, max+4). Depending upon the implement you use (per list below) you also gain certain benefits if it is a magical implement:
Amulet/Medallion/Necklace : Must be worn for all benefits. You may use reaction to gain implement bonus to one physical stat save or ability check (ST, DX, CN) equal to your implement bonus / 1 Long rest
Book, Scroll, Tome: Add your implement bonus to one skill and/or tool proficiency checks you are proficient in already, your choice. When the book is in your hands (both), you also gain one extra spell slot per long rest, for a level maximum equal to your proficiency bonus -1 (Max 5th level). You also may cast one cantrip as a bonus action, once per short rest.
Boots/Shoes: Must be worn, but you may use your reaction to gain a Dash action usable during someone else's turn once per long rest
Bracers/Bracelet/Gloves: Must be worn - use your reaction to gain a bonus to your AC until end of your next turn equal to your implement bonus, or as a bonus action to gain the bonus to an attack roll. Once either is used, recharges with a long rest
Cloak/Cape: Must be worn, you gain a bonus equal to your implement bonus to concentration checks to preserve spells. You also may change the coloring of your implement once per long rest as you see fit
Gem/Jewel / Stone: Must be wielded in one hand to use. Gain advantage on one spell attack roll and/or spell caster check per long rest.
Headband/Helm/Hat: Must be worn to use. Use reaction to gain bonus to one mental stat (IN, WI, CH) save or ability check equal to your implement bonus / once per long rest
Musical Instrument: Must be in both hands to use. Gain implement bonus to all perform checks with the instrument. You also gain a shield bonus equal to your implement bonus. Once per long rest, cast one 1st level or cantrip spell dependent upon voice and/or with thunder damage as a bonus action.
Ring: Must be worn for benefit. Use a bonus action when you cast a spell, to double the maximum duration of any spell once per long rest
Robe/Vest/Clothing: When you cast a spell that grants you a bonus to AC, you may use a bonus action to increase it +1 AC once per long rest. Your worn implement provides you protection from the elements as if you were wearing furs in Cold conditions
Staff: Must be in hand for benefit. Specify one first level spell that you prepare after each long rest. Your staff may store that spell for an extra re-casting until your next long rest.
Statue / Idol / Skull / Relic: Must be in your hand to benefit. Add your implement bonus on saves against possession, gaze, or visual-dependent attacks. Also, Pick one spell you can cast that inflicts damage and/or a condition upon others once per long rest. that you know. You are immune to that spell anytime you choose to be.
Tatoo, Mark, Piercing: Gain a free cantrip with a range of touch or selfto add to your spell list
Token / Bauble / Other Wonderous Item: Must be in your hand to benefit. Substitute for any material component or spell focus of up to 50 gp value. Also, pick one first level spell known from another classes spell list (Wizard, Cleric, Druid, Warlock, Sorcerer, Bard) you may add to your list of available spells
Torch, Lantern, Candle: Must be in hand to benefit. The light source never runs out of fuel fom being burned for light. Also as a bonus action, the light from your implement negates any magical darkness in a 20' radius at a max level equal to your implement bonus until beginning of your next turn once per long rest.
Wand or Rod: Must be in your hand. Add your implement bonus to damage, or healing of damage to any spell you cast
Weapon: You can convert a weapon with a bonus to an implement bonus to spell attacks. On a critical hit, your weapon inflicts +1d8 force damage.